Clays & Charcoal · Clay
French Green Clay
Illite and iron-rich smectite clay (a mineral mixture, not a plant) · also called French green clay, argile verte, sea-green clay (shop names)
French green clay is a green clay powder sold for face masks and, by some sellers, for swallowing. The two studied for healing were mostly illite and iron-rich smectite. Evidence is lab and animal work and a few reports, with no trial of a green clay mask or of swallowing it. Green clays have held arsenic, lead and mercury, so safety comes first.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About French Green Clay
French green clay is a trade name for a green clay mostly made of illite and iron-rich smectite. Research is lab, mouse and observation only. Two similar clays acted oppositely on bacteria. Some green clays held lead, arsenic and mercury. No trial supports detox, swallowing or masks for acne with this clay.
What it is
"French green clay" is a shop name. The two clays studied for healing were dominated by 1Md illite and iron-rich smectite. Smectite is the group that montmorillonite belongs to.
Two clays that looked alike in mineral tests behaved in opposite ways against bacteria: one killed them and one helped them grow. So colour and name do not tell you what a jar does.
Traditional and current uses
Clay has been put on skin for healing since early recorded history. In Ivory Coast a field worker reported about ten years of French green clay poultices on advanced Buruli ulcer to the World Health Organization in 2002. She could not run controlled studies for lack of funding.
Today it is sold as a face-mask powder and, by some sellers, to swallow. Traditional use is not proof that it works or is safe.
What the research shows
Lab work suggests that wet clay changes pH and oxidation state so that iron stays dissolved, and that this can kill some bacteria. A green clay lost the effect when neutralised.
In mice, hydrated clay poultices (other clays) were followed by healing and fewer Buruli ulcer bacteria. In people there are observations, not trials.
The only human trial-type study read is a 75-person, 4-week study of a different branded clay mask. It reported less oil and fewer acne signs but its abstract describes no comparison group, and the authors work for the maker.
At a glance
Traditional uses history, not proof
- Put on the skin for healing since the earliest recorded history (Williams and Haydel 2010).
- Poultices on advanced Buruli ulcer in Ivory Coast, reported to the World Health Organization in 2002 (described in the 2010 review).
- Clay eating (geophagy) has been seen in all parts of the world since antiquity (Gomes 2018).
Studied for research
- Face masks for oily skin and acne, insufficient evidence for this clay
- Killing bacteria in the lab, very low (lab only)
- Poultices on skin ulcers, insufficient (observations and mice)
- Detox or drawing out toxins, insufficient
- Swallowing for digestion, insufficient (risks reported)
- Skin-type cells in a dish, very low (cell work only)
Main compounds
- Illite (clay mineral)
- Iron-rich smectite (clay mineral)
- Iron, which in the lab appeared to drive bacteria-killing
- Contaminant metals in some samples: arsenic, lead, mercury
Common forms
- Dry powder
- Mask paste mixed with water
- Poultice (damp clay on skin; observed in Buruli ulcer care)
- Swallowed in water (not supported by the sources read)
Research links: Healing clays review, 2010 (full text) · Lead and arsenic in green clay on mouse skin, 2020 (abstract) · Mercury in cosmetic clays, 2025 (abstract) · NCCIH: Detoxes and cleanses · Poison Control · Research Library · Genes & Biomarkers Library
What it is and its history
- Accepted scientific name
- French green clay (trade name; a mixed-mineral clay, not a single mineral)
- Synonyms
- Illite-smectite green clay; Sea-green clay (shop name)
- Common names
- French green clay (English); Argile verte (French)
- Family or group
- Clay mineral mixture: illite with iron-rich smectite (smectite is the group montmorillonite belongs to)
- Native range
- Deposits in France and elsewhere; the two studied clays were supplied to a worker in Ivory Coast by different suppliers (2010 full text).
- Habitat
- Mined from sediment deposits.
- Harvest and processing
- Dug, dried and ground to a powder. Processing differs by supplier; not checked beyond that.
- Look-alikes and adulterants
- Name: Other green or 'healing' clays; Note: Two clays with similar minerals behaved in opposite ways against bacteria, so a result for one named clay should not be applied to any jar (2008, 2010).
Traditional use and history history, not clinical proof
| Tradition or era | Documented use | Source |
|---|---|---|
| Ancient to modern | Clays have been used to heal skin infections since the earliest recorded history (Williams and Haydel 2010). Clay eating has been seen in all parts of the world since antiquity (Gomes 2018). | p20640226 |
| Ivory Coast, reported to WHO in 2002 | A field worker used French green clays on advanced Buruli ulcer and in 2002 reported about 10 years of this work to the World Health Organization; she could not do controlled experiments for lack of funding. | p20640226 |
Traditional use shows how it was used. It does not show that it works or is safe today.
What is inside, and how it may work
What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.
Main compounds
| Compound | Family | Where it is concentrated | Activity studied | Level of evidence |
|---|---|---|---|---|
| Illite | clay mineral | Dominant in the two French green clays studied (as 1Md illite). | Mineral structure; no drug-like activity described. 9 | Laboratory |
| Iron-rich smectite | clay mineral | Dominant with illite in the two clays. | Swelling clay with high surface area; buffers pH and oxidation state in water (2008, 2011). 9 11 | Laboratory |
| Dissolved iron (Fe2+) | metal ion | Iron measured at 44,750 and 56,300 ppm in the two samples (2010 full text). | Proposed in the 2011 paper to kill bacteria by lethal hydroxyl radicals. 11 10 | Laboratory |
| Arsenic, lead, mercury (contaminant metals) | toxic elements | Arsenic 43.3 and 5.5 ppm in two samples; mercury mean 28.91 micrograms per kilogram in cosmetic clays. | Toxic elements, not active ingredients. 10 4 | Product analysis |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Bacterial iron overload (proposed) | None | Clay buffers pH and oxidation state so Fe2+ stays dissolved; iron then enters bacteria and makes hydroxyl radicals. Seen in E. coli in the lab. 11 9 | Laboratory |
| Adsorption of oils and toxins | None | Clay particles can bind substances, but could also bind heavy metals and make them available for uptake. 5 10 | Narrative review |
| pH-dependent activity | None | A green clay killed bacteria only as a wet suspension and lost the effect when neutralised. 6 | Laboratory |
Absorption, metabolism and elimination
- Absorption
- Not studied for French green clay. Clay minerals are not known to be absorbed whole; metals in the clay may be taken up (Gomes 2018, theory).
- Distribution
- Lead rose in mouse liver and kidney after skin application (2020).
- Elimination
- Not studied.
- Bioavailability
- Not studied.
Isolated compounds versus whole extracts
Whole clay, its leachate (clay-soaked water) and neutralised clay behave differently in the lab: leachates were often less antibacterial than suspensions, and neutralising removed the effect in one green clay.
Nutritional composition
Clay is not a food or nutrient. A review citing older data says eaten clay has been reported to supply small shares of some minerals but can also block iron, zinc and potassium; nothing like that was shown for French green clay.
2 very low certainty5 not enough evidence
What was looked at
The 7 benefits and uses checked for French Green Clay, each with how strong the evidence is. Tap one to open it.
- Face masks for oily skin and acneNot enough evidence
- Killing bacteria in the labVery low certainty
- Poultices on skin ulcers (Buruli ulcer)Not enough evidence
- Detox or "drawing out toxins"Not enough evidence
- Swallowing clay for digestion or "cleansing"Not enough evidence
- "Rich in minerals"Not enough evidence
- Effects on skin-type cells in a dishVery low certainty
Lab markers tracked in the studies
Skin oil (sebum) on a skin-oil meterBacterial survival in wet clay (lab count)M. ulcerans in infected mouse tail woundsArsenic in the clay (parts per million)
What is French Green Clay good for?
The uses people ask about and how strong the evidence is for each. None is proven for French green clay, and the lab results do not show benefit in people.
Benefits, one by one
Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.
Face masks for oily skin and acne
Not enough evidenceNo study of a French green clay mask in people was found. One 4-week study of a branded kaolin-and-bentonite-type clay mask in 75 adults reported less oil and fewer acne signs, but it had no comparison group and was run by the maker.
2 studiesBranded mask used twice a week in the study; not advice.
Studies, doses and limits
What the trials found
One uncontrolled 75-person study of a branded clay mask (La Roche-Posay Effaclar; the abstract names kaolin and bentonite as the clays of interest, not green clay). Nothing on French green clay masks in people was found.
Results
Over 4 weeks of twice-weekly use the authors report significant improvements in acne-related outcomes, sebum, skin evenness and skin water content. Pore area and porphyrin area did not change significantly.
Effect sizes as reported
No effect sizes in the abstract.
Why this rating
No trial of French green clay on skin. The one human study of a different clay mask had no comparison group in its abstract, used partly self-reported outcomes, and its authors work for the maker.
Form and dose studied
Branded mask used twice a week in the study; not advice.
Who was studied
Adults with oily or combination skin (China).
Limits
No control group described; industry-linked; a different clay product; short.
Why researchers looked
Sellers say green clay draws out oil and impurities from the skin. Companies test clay masks for oily skin and acne.
Traditional use
Clays have been put on the skin for healing since the earliest recorded history (Williams and Haydel 2010).
Proposed mechanism Pharmacological theory
Clays soak up water and oils because of their large surface area and fine particles (2010 review). That is a property of the powder, not proof of an effect on acne.
A proposed mechanism does not show that the effect happens in people.
Green clays have contained arsenic, lead and mercury (see the Safety tab). Patch-test and stop if skin reacts; ask a pharmacist or doctor about acne.
Killing bacteria in the lab
Very low certaintyIn test tubes, one French green clay killed several bacteria and a similar-looking second clay helped them grow. This is lab work only and does not show a mask treats infection.
4 studiesWet clay suspensions and leachates in dishes; no human preparation.
Studies, doses and limits
Results
Two French green clays with similar minerals (mostly illite and iron-rich smectite) had opposite effects: one promoted bacterial growth, one killed bacteria (2008, 2010). Leachates (clay-soaked water) of antibacterial clays killed E. coli (2011). A separate 2021 study found a green clay killed bacteria only as a wet suspension and lost the effect when neutralised; filtered leachates held too few ions to kill bacteria.
Why this rating
Lab only. Few samples. The effect depends on the deposit, the water and the pH, so one named clay cannot be assumed to behave like another jar.
Form and dose studied
Wet clay suspensions and leachates in dishes; no human preparation.
Who was studied
Bacteria and cell lines.
Limits
Results from a small number of clay samples; some of the work is from the same research group; no human trial.
Why researchers looked
Scientists were asked to explain reports that French green clay poultices helped people with a severe skin infection called Buruli ulcer.
Traditional use
A field worker in Ivory Coast reported about 10 years of clay use on advanced Buruli ulcer to the World Health Organization in 2002 (as described in the 2010 review).
Proposed mechanism Laboratory
The clay wets to a certain pH and oxidation state that keeps dissolved iron (Fe2+) available. The authors propose that iron enters bacterial cells and makes lethal hydroxyl radicals. The effect is chemical, not a physical sticking of bacteria to clay.
A proposed mechanism does not show that the effect happens in people.
Lab killing of bacteria does not make clay a safe treatment for an infection. Seek medical care for a skin infection.
Poultices on skin ulcers (Buruli ulcer)
Not enough evidenceReports from West Africa describe healing after French green clay poultices on Buruli ulcers, but they are observations, not trials. A mouse study of other hydrated clays saw healing and fewer bacteria in infected tails.
3 studiesHydrated clay poultice (mice); not advice.
Studies, doses and limits
What the trials found
Case observations and photographs described in the 2010 review; the field worker could not carry out controlled experiments for lack of funding. No trial.
Results
In mice with Buruli ulcer-type tail infection, daily hydrated CB09 clay poultices for 22 days were followed by healing by appearance and fewer M. ulcerans in the wounds. The abstract does not state that CB09 is a French green clay.
Effect sizes as reported
No numbers in the abstract.
Why this rating
No controlled human study. The mouse clays are not stated to be French green clay. Number of mice not given in the abstract.
Form and dose studied
Hydrated clay poultice (mice); not advice.
Who was studied
Mice; human case reports.
Limits
Anecdotes and one mouse model; different clays; the authors only say poultices "may" help.
Why researchers looked
Buruli ulcer is a severe skin infection caused by Mycobacterium ulcerans and surgery or antibiotics are not always available where it is common.
Traditional use
Documented clinical use of French green clay on advanced Buruli ulcer in Ivory Coast (2010 review, citing a 2002 WHO report).
Proposed mechanism Laboratory
Proposed as antibacterial chemistry of the wet clay (see above).
A proposed mechanism does not show that the effect happens in people.
Never use clay instead of medical treatment for an ulcer or wound. Green clay has contained lead and arsenic and lead built up in mouse liver and kidney after skin use.
Detox or "drawing out toxins"
Not enough evidenceNo study shows French green clay removes toxins from the body. A health agency says there is no compelling research that detox diets do this.
2 studiesNot applicable.
Studies, doses and limits
What the trials found
No human study of French green clay for detox was found.
Results
NCCIH reports that a 2015 review found no compelling research that detox diets remove toxins. That statement is about detox diets generally, not about clay.
Why this rating
No human data on green clay for this claim.
Limits
Absence of evidence; the agency statement is general.
Why researchers looked
Sellers say clay binds toxins. Clay particles can bind some substances in a dish, and the idea is carried over to the body.
Traditional use
Eating or using clay for health is very old (Gomes 2018).
Proposed mechanism Pharmacological theory
Clay particles could adsorb toxic substances so they leave the body, but could also adsorb heavy metals and make them available for uptake (Gomes 2018 review abstract). No test in people was found.
A proposed mechanism does not show that the effect happens in people.
Eating green clay is not supported and some samples held arsenic, lead and mercury; see the Safety tab.
Swallowing clay for digestion or "cleansing"
Not enough evidenceNo trial of swallowing French green clay was found. Reviews warn that large amounts of eaten clay can block iron, zinc and potassium, and that safety of clay eating is not established.
3 studiesNone advised. The 200 g figure is a level at which harm was reported,…
Studies, doses and limits
What the trials found
Reviews of people who eat clay; no trial of French green clay.
Results
The 2010 review says clay eaten at more than 200 grams a day, especially high-exchange clay, can impede iron, zinc and potassium absorption and lead to deficiencies. The 2022 geophagia review says the safety of clay eating is not fully established, toxicity has been poorly investigated, and some minerals found in clays are toxic if eaten.
Why this rating
No trial; reviews describe risks rather than benefits.
Who was studied
People who habitually eat clay.
Limits
The reviews mostly cover soil-eating, not cosmetic green clay powder.
Why researchers looked
Clay eating (geophagy) is old and common in many places, including during pregnancy for nausea.
Traditional use
Clay eating (geophagy) has been observed in all parts of the world since antiquity (Gomes 2018 abstract).
Proposed mechanism Pharmacological theory
Clay with high cation-exchange capacity can hold on to minerals in the gut (2010 review).
A proposed mechanism does not show that the effect happens in people.
Do not swallow cosmetic clay. If someone has, call poison control (see Safety tab).
"Rich in minerals"
Not enough evidenceLab tables show French green clay holds iron, magnesium and potassium, but it also held arsenic. Nothing shows the body takes up useful amounts from a mask.
2 studiesNot applicable.
Studies, doses and limits
Results
In the 2010 review's full-text table, the antibacterial French green clay held 44,750 ppm iron and 43.3 ppm arsenic; its non-antibacterial twin held 56,300 ppm iron and 5.5 ppm arsenic. The authors say the key antibacterial agent is likely a trace element or transition metal.
Why this rating
Composition of two samples only; no test of uptake by people.
Who was studied
Two clay samples.
Limits
Two samples from 2000s deposits; today's products may differ.
Why researchers looked
Sellers describe green clay as mineral-rich.
Traditional use
Not described in the sources read.
Proposed mechanism Laboratory
Minerals are locked in the clay structure and in exchangeable form; what leaves the clay depends on pH and water.
A proposed mechanism does not show that the effect happens in people.
Mineral content can include toxic metals; see the Safety tab.
Effects on skin-type cells in a dish
Very low certaintyIn cell dishes, clay water stimulated wound-healing responses in skin-type cells, and refined montmorillonite was more harmful to gut-type cells than skin-type cells when amounts were high.
2 studiesNot applicable.
Studies, doses and limits
Results
Many clay leachates stimulated wound-healing responses in HaCaT skin-type cells (2021, includes a green clay) while all leachates were toxic to THP-1 immune cells. A 2024 study of refined montmorillonite (a related clay) linked side effects in colon-type and skin-type cells to excess amounts and silica sand.
Why this rating
Cells in a dish; mixed results; related clays.
Who was studied
Cell lines.
Limits
Cells are not skin; the 2024 clay is not green clay.
Why researchers looked
To check whether clays help or harm human cells.
Traditional use
Not described in the sources read.
Proposed mechanism Laboratory
Unclear; the 2021 authors point to pH and clay surface charge.
A proposed mechanism does not show that the effect happens in people.
Mixed signals in cells are a reason for caution, not a reassurance.
Connections to the rest of health
How French Green Clay connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.
Explore every connection: goals, body systems, organs, symptoms, genes
A. Wellness goals
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Healthy Skin | Not enough evidence | Face masks for oily skin and acne: No study of a French green clay mask in people was found. One 4-week study of a branded kaolin-and-bentonite-type clay mask in 75 adults reported less oil and fewer acne signs, but it had no comparison group and was run by the maker. | 12 10 | |
| Healthy Skin | Very low certainty | Killing bacteria in the lab: In test tubes, one French green clay killed several bacteria and a similar-looking second clay helped them grow. This is lab work only and does not show a mask treats infection. | 9 10 11 6 | |
| Healthy Skin | Not enough evidence | Poultices on skin ulcers (Buruli ulcer): Reports from West Africa describe healing after French green clay poultices on Buruli ulcers, but they are observations, not trials. A mouse study of other hydrated clays saw healing and fewer bacteria in infected tails. | 10 1 9 | |
| Detoxification Support | Not enough evidence | Detox or "drawing out toxins": No study shows French green clay removes toxins from the body. A health agency says there is no compelling research that detox diets do this. | 13 5 | |
| Digestive Support | Not enough evidence | Swallowing clay for digestion or "cleansing": No trial of swallowing French green clay was found. Reviews warn that large amounts of eaten clay can block iron, zinc and potassium, and that safety of clay eating is not established. | 10 2 5 |
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Integumentary System | Biological association | Not enough evidence | Studied for: Face masks for oily skin and acne Studied for: Poultices on skin ulcers (Buruli ulcer) | 12 10 1 9 6 7 |
| Immune System | Biological association | Very low certainty | Studied for: Killing bacteria in the lab | 9 10 11 6 |
| Digestive System | Biological association | Not enough evidence | Studied for: Detox or "drawing out toxins" Studied for: Swallowing clay for digestion or "cleansing" | 13 5 10 2 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Skin oil (sebum) on a skin-oil meter | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 12 |
| Bacterial survival in wet clay (lab count) | Biological association | Very low certainty | Measured in trials: lowered (one clay) or raised (a twin clay). A lab change is not the same as a health benefit. | 9 6 |
| M. ulcerans in infected mouse tail wounds | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 1 |
| Arsenic in the clay (parts per million) | Biological association | Very low certainty | Measured in trials: higher in the antibacterial sample. A lab change is not the same as a health benefit. | 10 |
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Illite | Biological association | Laboratory | Mineral structure; no drug-like activity described. | 9 |
| Iron-rich smectite | Biological association | Laboratory | Swelling clay with high surface area; buffers pH and oxidation state in water (2008, 2011). | 9 11 |
| Dissolved iron (Fe2+) | Biological association | Laboratory | Proposed in the 2011 paper to kill bacteria by lethal hydroxyl radicals. | 11 10 |
| Arsenic, lead, mercury (contaminant metals) | Biological association | Product analysis | Toxic elements, not active ingredients. | 10 4 |
Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 25, 2026).
Evidence at a glance: what changed in 2 lab markers
Tap a number to show only those markers. Counts are markers, not people.
The evidence
The research centre for French Green Clay. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).
How we rate evidence
High certainty
Several well-run trials or reviews agree; further research is unlikely to change the picture much.
Moderate certainty
Good trials point the same way, but some doubt remains.
Low certainty
Small, short or inconsistent trials. The finding could change with better research.
Very low certainty
Very little or very weak human data. Treat as a possibility only.
Mixed findings
Trials or reviews disagree with each other.
Not enough evidence
Not enough human research to say either way.
Evidence against
Good research found no benefit, or found harm.
We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We searched PubMed, read the abstract of each cited paper, read the 2010 healing-clay review in full text on PubMed Central, and read the FDA cosmetics, NCCIH detox and Poison Control pages. Certainty ratings are the compiler's own reading. One study is from a mask maker's staff and is flagged. Regulators outside the US and EFSA beyond one abstract were not checked. No study is cited that we could not verify.
Study library: every study we checked 15
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Adusumilli 2016 In vitro antibacterial activity and in vivo efficacy of hydrated clays on Mycobacterium ulcerans growth BMC Complementary and Alternative Medicine · PMID 26833071 · DOI |
Animal study animal |
Lab dishes with M. ulcerans, and mice with M. ulcerans infection in the tail (Buruli ulcer model) | Hydrated clay mixtures CB07 to CB10 and BY07 (named by code; not stated to be French green clay in the abstract) mineral clay (not a plant) 10% clay suspensions in the lab; hydrated CB09 poultice on mouse tails 22 days of daily poultices (five days a week) in mice |
CB07, CB08 and CB09 killed M. ulcerans over 7 to 28 days; leachates only slowed its growth. Mice given CB09 poultices showed healing by gross appearance and fewer M. ulcerans in the wounds. The authors conclude hydrated clay poultices "may offer" a complementary strategy. Methods, limits and fundingOutcomes: Survival of M. ulcerans over 28 days; healing and bacterial load in infected mouse tails Limitations: Mouse tails and lab dishes. The abstract does not say these clays were French green clays. Number of mice not given in the abstract. Funding and conflicts: PubMed lists NIH extramural research support. No conflict statement in the abstract. Read: abstract |
| Bonglaisin 2022 Geophagia: Benefits and potential toxicity to human - A review Frontiers in Public Health · PMID 35958861 · DOI |
Narrative review |
Review of people who eat clay soil such as chalk or kaolin | Eaten clay soils (geophagy), mostly kaolin-type and local soils mineral clay (not a plant) |
The review says the safety of people who eat clay is not fully established. Published studies lack adequate investigation of toxicity; some identified minerals are toxic if eaten, mostly from detecting those elements in the clay, not from measuring harm in people. Clay content varies by source. The authors call for more metabolic studies. Methods, limits and fundingOutcomes: Safety of eating clay Limitations: Mostly about soil-eating traditions, not about cosmetic or "wellness" green clay powder. Abstract only. Funding and conflicts: No conflicts declared. Read: abstract |
| EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) 2026 Assessment of a feed additive consisting of montmorillonite-illite mixed layer clay mineral (1g557) for all animal species for the renewal of its authorisation (FIM Biotech GmbH) EFSA Journal · PMID 42564637 · DOI |
Authoritative guidance n/a |
A regulator opinion on an animal feed additive, not a cosmetic or a human product | Montmorillonite-illite mixed-layer clay as animal feed additive mineral clay (not a plant) |
The panel could not conclude whether the additive remains safe for the target animals. It judged it safe for consumers and the environment under current conditions. It says the additive should be considered a skin and respiratory sensitiser, that it could not conclude on eye irritation for lack of data, and that exposure of users by any route is a risk and should be minimised. Methods, limits and fundingOutcomes: Safety for animals, consumers, users and environment Limitations: About a related illite-smectite type clay used in animal feed; it is not about French green clay masks. Funding and conflicts: EFSA regulator opinion; the application came from a company (FIM Biotech GmbH). Read: abstract |
| Fischer 2025 Analysis of Mercury Concentration in Cosmetic Clays Toxics · PMID 40559980 · DOI |
Product analysis product |
Cosmetic clays of different colours from different makers on the Polish market (number of samples not given in the abstract) | Cosmetic clays analysed for mercury mineral clay (not a plant) |
Mercury was found in all samples: mean 28.91 micrograms per kilogram, range 1.87 to 200.81. The highest averages were in green clays (53.26) and white clays (52.80); the lowest in purple (2.56) and blue (3.69). Differences between types were statistically significant. The authors say such products likely need metal testing. Methods, limits and fundingOutcomes: Mercury content by clay colour Limitations: One country, one laboratory; the abstract gives no sample count and does not say these were French green clay. The abstract gives no health-risk calculation. Funding and conflicts: No conflicts declared. Read: abstract |
| Gomes 2018 Healing and edible clays: a review of basic concepts, benefits and risks Environmental Geochemistry and Health · PMID 28150053 · DOI |
Narrative review |
Review of healing clays for therapy and skin care, and of edible clays | Healing and edible clays in general mineral clay (not a plant) |
The review says clay particles could adsorb toxic substances so that they leave the body, but could also adsorb toxic elements such as heavy metals and make them available for uptake through eating or through the skin. It also says healing clays could bring important health and skin-care risks. The abstract gives no numbers. Methods, limits and fundingOutcomes: Benefits and risks of healing clays Limitations: Abstract only; general to healing clays, not French green clay in particular. Funding and conflicts: No conflict statement in the abstract. Read: abstract |
| Incledion 2021 A New Look at the Purported Health Benefits of Commercial and Natural Clays Biomolecules · PMID 33466399 · DOI |
Lab study lab |
Clays sold or proposed as antibacterial, tested on wound bacteria and on human immune-type (THP-1) and skin-type (HaCaT) cell lines | Commercial and natural clays, including one "Green" clay, as particles, suspensions and filtered leachates mineral clay (not a plant) |
All clays held minerals with antibacterial potential, but the filtered leachates held too few ions to kill bacteria. All leachates were toxic to THP-1 immune cells, suspensions less so. Toxicity to HaCaT skin-type cells was lower and many leachates stimulated wound-healing responses in the cell dish. The "Green" clay killed bacteria only as a wet suspension, and lost that when neutralised. The authors say pH and clay surface charge matter more than thought, and warn about unregulated marketing and unsubstantiated "bioceutical" claims. Methods, limits and fundingOutcomes: Antibacterial effect, cell toxicity, cell survival and scratch-wound closure in cells Limitations: Cell and bacteria work; the clays are described only by trade colour in the abstract, so the green clay cannot be matched to every French green clay product. Funding and conflicts: No conflict of interest declared. Read: abstract |
| Wang 2024 Toxicological Evaluation toward Refined Montmorillonite with Human Colon Associated Cells and Human Skin Associated Cells Journal of Functional Biomaterials · PMID 38535268 · DOI |
Lab study lab |
Three commercial montmorillonite samples, refined by size, tested on human colon-type and skin-type cells | Refined montmorillonite (a related smectite clay, not French green clay) mineral clay (not a plant) |
Side effects in the cells were linked to excess amounts and to silica sand. They were more obvious in the colon-type cells than in the skin-type cells. Cell interactions were linked to particle size. Methods, limits and fundingOutcomes: Cell toxicity and cell-clay interactions by clay size Limitations: Cell work on a related clay; no people. Funding and conflicts: No conflicts declared. Read: abstract |
| Whiteside 2020 Elevated Arsenic and Lead Concentrations in Natural Healing Clay Applied Topically as a Treatment for Ulcerative Dermatitis in Mice Journal of the American Association for Laboratory Animal Science · PMID 32059757 · DOI |
Animal study animal |
40 Two groups of 20 shaved adult male CD1 mice without skin disease |
Green clay paste applied to the skin daily mineral clay (not a plant) 2 weeks · vs Saline |
The clay product held high concentrations of arsenic and lead. After two weeks of daily skin application, lead was higher in liver and kidney of clay-treated mice than in controls, in both groups. Arsenic in liver and kidney did not differ. The lead-sensitive enzyme (delta-aminolevulinate dehydratase) did not differ, and the authors report no measurable biological effect. They say the products should be used with caution. Methods, limits and fundingOutcomes: Arsenic and lead in liver, kidney and blood; a lead-sensitive enzyme Limitations: Mice, not people. Shaved but healthy skin. Short exposure. The abstract says "green clays" in general; the product is not named as French green clay. Funding and conflicts: Intramural US government (NIEHS) research. No conflict statement in the abstract. Read: abstract |
| Williams 2008 Chemical and mineralogical characteristics of French green clays used for healing Clays and Clay Minerals · PMID 19079803 · DOI |
Lab study lab |
2 Two commercial French green clays used for Buruli ulcer care in Ivory Coast |
Two French green clays tested against a broad range of bacteria mineral clay (not a plant) |
One clay promoted bacterial growth and the other killed or strongly slowed it. Both were mostly 1Md illite and iron-rich smectite. The authors conclude that the clay chemistry, and surface properties that set pH and oxidation state, control the chemistry of the water used to wet the clay and supply the antibacterial agent. Methods, limits and fundingOutcomes: Mineral and chemical make-up of two French green clays; effect on bacteria in the lab Limitations: Two clay samples only; lab work, not people. Funding and conflicts: Not stated in the abstract. Read: abstract |
| Williams 2010 Evaluation of the medicinal use of clay minerals as antibacterial agents International Geology Review · PMID 20640226 · DOI |
Narrative review lab |
Review of clay use for skin infection, with lab tests of French green clays and other healing clays | French green clays and other healing clays (lab testing and review) mineral clay (not a plant) |
Of the clays tested, three killed a broad range of human bacteria. Two French green clays that were similar in mineral make-up had opposite effects: one promoted bacterial growth and one killed bacteria. The authors say the killing is chemical, not physical, and the cause was still under investigation. The full text says scientific evidence of clays treating ulcers, tumors, cysts, cancers and osteoporosis is lacking, that reports of Buruli ulcer healing came from a field worker's documentation to the World Health Organization and not from controlled experiments, that clay eaten at more than 200 grams a day, especially clay with high cation-exchange capacity, can impede absorption of iron, zinc and potassium, and that the US FDA does not require pre-market approval of cosmetics. In the antibacterial sample arsenic was 43.3 ppm versus 5.5 ppm in the non-antibacterial twin (full-text table). Methods, limits and fundingOutcomes: Which clays kill bacteria in the lab and why; how healing clays have been used Limitations: A review by the same group that made the lab findings; the Buruli ulcer reports are observations, not trials. Funding and conflicts: Not stated in the abstract. Read: full-text |
| Williams 2011 What makes a natural clay antibacterial? Environmental Science and Technology · PMID 21413758 · DOI |
Lab study lab |
Natural clays that kill bacteria in the lab, compared with clays that do not | Natural antibacterial clays and their water leachates mineral clay (not a plant) |
Natural antibacterial clays held very fine (under 200 nm) illite-smectite and reduced iron. The clay buffers pH and oxidation state so that dissolved iron (Fe2+) stays available. In E. coli killed by leachates, iron and phosphorus inside the cells were higher than in controls. The authors propose that iron overwhelms the cell's controls and produces lethal hydroxyl radicals. Methods, limits and fundingOutcomes: What features and chemistry separate antibacterial clays from others Limitations: Lab work on bacteria in water; does not show effect on skin or in people. Funding and conflicts: PubMed lists NIH extramural and non-US government research support. No conflict statement in the abstract. Read: abstract |
| Zhang 2023 Comprehensive assessment of the efficacy and safety of a clay mask in oily and acne skin Skin Research and Technology · PMID 38009030 · DOI |
Uncontrolled trial |
75 75 adults with oily or combination skin |
One brand-name clay mask (the abstract names kaolin and bentonite as the clays of interest; it does not say the mask held French green clay) mineral clay (not a plant) Twice a week 4 weeks |
Over 4 weeks the authors report significant improvements in acne-related outcomes, sebum content, skin evenness, skin water content and water loss through the skin. Pore area and porphyrin area did not change significantly. They report reduced dryness and irritation and high product acceptability. Methods, limits and fundingOutcomes: Acne lesions, sebum, hydration, skin irritation, pores Limitations: The abstract describes no comparison group, so improvement cannot be credited to the clay alone. The mask is a branded cosmetic, not French green clay. Self-assessment was part of the outcome. Funding and conflicts: Authors work for L'Oreal (maker of the tested mask); the paper reports no conflict of interest. Treat as industry-linked. Read: abstract |
| n/a 2025 NCCIH (NIH): Detoxes and Cleanses: What You Need To Know (last updated March 2025) n/a · Source |
Authoritative guidance n/a |
n/a | n/a |
Says a 2015 review concluded there was no compelling research to support "detox" diets for weight management or for eliminating toxins from the body. The page is about detox diets and cleanses in general and does not mention clay in the passage read. Methods, limits and fundingOutcomes: Whether "detox" products and diets remove toxins Limitations: A health agency fact sheet about detoxes in general, not a clay study. Read: full-text |
| n/a 2025 FDA: FDA Authority Over Cosmetics: How Cosmetics Are Not FDA-Approved, but Are FDA-Regulated (content current as of 11/18/2025) n/a · Source |
Authoritative guidance n/a |
n/a | n/a |
Says cosmetic products and ingredients do not need FDA premarket approval, except colour additives, but FDA can take enforcement action against products on the market that do not comply with the law. Methods, limits and fundingOutcomes: How the US regulates cosmetics Limitations: Explains cosmetics law in general; it does not mention French green clay. Read: full-text |
| n/a 2026 Poison Control (National Capital Poison Center): home page, read 2026-10-25 n/a · Source |
Authoritative guidance n/a |
n/a | n/a |
Says help is free and confidential online and by phone at 1-800-222-1222 (US), and to call 911 if the person collapses, has a seizure, has trouble breathing or cannot be woken. Methods, limits and fundingOutcomes: What to do after a poisoning Limitations: Service information, not research. Read: full-text |
What we do not know yet
- No controlled trial of a French green clay mask on oily or acne skin.
- No trial of any clay poultice on a skin ulcer in people.
- No human data on swallowing French green clay, in pregnancy, in children or with medicines.
- No testing of today's retail products against the lab-tested deposits for metals.
How new research is added
New studies are found by a saved PubMed search and are placed in a review queue. A person reads each one before it changes any evidence rating or safety wording.
Lab markers
What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".
Other 4
Skin oil (sebum) on a skin-oil meter
Lowered in trials
How much oil sits on the skin surface, measured with a small probe. High values go with oily skin.
Very low certaintyResults and what it means
Why it was measured
To test whether a mask reduces shine and oiliness.
Statistical vs. clinical meaning
Statistically significant per the authors, but uncontrolled and from a mask maker, and not French green clay.
Safety implication
Reduced dryness and irritation reported by the authors.
| Study | Result | People | Product |
|---|---|---|---|
| 12 | Sebum content improved significantly over 4 weeks of twice-weekly use (no numbers in the abstract). | 75 adults with oily or combination skin | Branded clay mask versus no comparison group described |
Bacterial survival in wet clay (lab count)
Lowered (one clay) or raised (a twin clay) in trials
How many live bacteria remain after being mixed with clay in a dish over time.
Very low certaintyResults and what it means
Why it was measured
To test whether a clay is antibacterial.
Statistical vs. clinical meaning
Shows chemistry in a dish, not a treatment.
Safety implication
Lab effects occurred in wet, low-pH conditions that are not those of skin.
M. ulcerans in infected mouse tail wounds
Lowered in trials
The amount of Buruli ulcer bacteria recovered from a wound.
Very low certaintyResults and what it means
Why it was measured
To check if a poultice reduces infection in an animal.
Statistical vs. clinical meaning
Animal result with a clay not stated to be French green clay.
Safety implication
None stated.
| Study | Result | People | Product |
|---|---|---|---|
| 1 | Fewer M. ulcerans in wounds of clay-treated mice (no numbers in the abstract). | Mice with tail infection | Hydrated CB09 clay poultice, 22 days |
Arsenic in the clay (parts per million)
Higher in the antibacterial sample in trials
The amount of arsenic found by lab analysis in a clay sample.
Very low certaintyResults and what it means
Why it was measured
Arsenic is a toxic element; clay is dug from the ground and can carry it.
Statistical vs. clinical meaning
Two samples only.
Safety implication
Arsenic in a product is a safety concern for swallowing and for skin use over time.
| Study | Result | People | Product |
|---|---|---|---|
| 10 | 43.3 ppm in the antibacterial French green clay and 5.5 ppm in its non-antibacterial twin (full-text table). | Two clay samples | Lab analysis |
Safety
What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.
Main points to know 5
- Do not swallow it for a "detox". No study shows French green clay detoxes the body. Reviews warn that eating a lot of clay can block iron, zinc and potassium, and that the safety of eating clay is not established. Some green clays held arsenic, lead and mercury. Narrative review 10 2 5 13
- Metals are the main product risk. A green clay used on mouse skin for two weeks raised lead in the liver and kidney. In Polish cosmetic clays, mercury was found in every sample and was highest on average in green and white clays. Metal content differs by deposit and product. Animal and product analysis 8 4
- Dry powder can irritate skin and lungs. EFSA's 2026 opinion on a related montmorillonite-illite clay used in animal feed says it should be treated as a skin and respiratory sensitiser and that user exposure by any route should be minimised. That opinion is not about face masks, but it is a reason to avoid breathing the dust. Authoritative guidance 3
- Do not use clay in place of care for an infection or ulcer. Reports of healing under clay poultices are observations, and mouse work used other clays. A wound or ulcer that is not healing needs medical care. Case report and animal 10 1
- Cosmetic clay is not pre-approved. The FDA says cosmetic products and ingredients do not need premarket approval (except colour additives), though it can act against non-compliant products on the market. A label cannot tell you the metals content. Authoritative guidance 14 10
Side effects 5
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Lead build-up in liver and kidney after skin application (mice) The authors found no measurable biological effect in the lead-sensitive enzyme they checked. | Seen in both groups of 20 mice after 2 weeks of daily use | unknown Not tested | Animal study 8 |
| Skin and breathing sensitisation (related clay, feed additive) Eye irritation could not be judged for lack of data. | Not established | unknown Not stated | Authoritative guidance 3 |
| Cell toxicity in a dish (related clays) Related to excess amounts, silica sand and pH in the lab; stronger on colon-type cells. | Not established | unknown Not applicable | Laboratory 6 7 |
| Low iron, zinc and potassium with large long-term clay eating Describes clay eating, not a mask. | Reported at over 200 g a day of clay in older reports cited by a review | unknown Not stated | Narrative review 10 |
| No human adverse-event data for French green clay masks were found A 75-person study of a different clay mask reported reduced dryness and irritation, but it was an uncontrolled, maker-run study. | Not established | unknown n/a | Gap 12 |
Liver
No report of liver injury from French green clay was found. In mice, lead from green clay paste built up in liver and kidney after skin use (2 weeks, daily); the authors saw no measurable effect on the one lead-sensitive enzyme they tested. 8
How often. No rate in people. Not searched in LiverTox.
Monitoring. No monitoring advice was found.
This is a safety connection. It is not evidence that French Green Clay supports liver health.
Medicines and supplements 3
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Medicines taken by mouth (in general) prescription | Clays can bind other substances, which could in theory reduce how much of a medicine is absorbed if clay is swallowed. | No interaction study with French green clay was found. The Gomes 2018 review abstract says clay particles can adsorb substances, which is a theory here, not a measured drug interaction. | Pharmacological theory Not enough evidence 5 | If you take any medicine, do not swallow clay without asking a pharmacist. Ask before taking clay near medicine times. |
| Iron, zinc and potassium from food and supplements nutrient | Clay with high cation-exchange capacity may hold minerals in the gut. | A review says more than 200 g a day can impede absorption and lead to deficiencies. That is a very large amount and is not a use recommendation. | Narrative review Low certainty 10 | Avoid swallowing clay if you are low in iron, or pregnant, or have anaemia; ask a clinician. |
| Skin medicines or acne treatments topical | Not described in the sources read. | No study was found. | None found Not enough evidence | Ask a pharmacist or doctor before combining a clay mask with prescription skin products. |
Who should check first 6
| Situation | Advice | Evidence |
|---|---|---|
| Pregnancy and breastfeeding | No data on French green clay were found in the sources read. Not described is not proof of safety. Do not swallow clay; ask a clinician before using it. | Gap 2 |
| Babies and children | No data were found. Keep powder out of reach and do not let children swallow or breathe it. | Gap 3 |
| Open wounds, ulcers or skin infections | Do not self-treat with clay instead of care. Poultice reports are observations and the mouse work used other clays. | Case report and animal 10 1 |
| Anaemia, low iron or potassium, or kidney problems | Avoid swallowing clay. A review says large intakes can lower iron, zinc and potassium. No kidney-specific data on this clay were found; ask a clinician. | Narrative review 10 |
| Asthma or other lung conditions | Avoid breathing dry powder. EFSA treats a related illite-smectite clay as a respiratory sensitiser. | Authoritative guidance 3 |
| Allergy | No allergy reports were found for French green clay in the sources read; the related clay in the EFSA opinion is a skin sensitiser. Patch-test on a small patch of skin first. | Authoritative guidance 3 |
Overdose, product quality and regulators
Summary. Clay itself is not a plant, so there are no toxic plant parts. The concerns are metals in some samples and large amounts if swallowed.
Animal. Mice given green clay paste on the skin for two weeks had more lead in liver and kidney.
Human doses studied. No dose studies of French green clay in people were found.
High dose or long term signals. A review reports older findings of low iron, zinc and potassium with clay eaten at over 200 g a day.
Overdose response. If someone has swallowed a clay product and feels unwell, call poison control (US 1-800-222-1222) or your local emergency number. Call 911 for collapse, seizure or trouble breathing.
Genotoxicity. Not read.
Clay is dug from the ground and can carry metals. Labels rarely say which, so the colour or the name 'French green' tells you nothing about metals.
Lead and arsenic. A green clay product used on mice held high concentrations of arsenic and lead; lead rose in liver and kidney after skin use. 8
Mercury. All Polish-market cosmetic clays tested held mercury (mean 28.91, range 1.87 to 200.81 micrograms per kilogram), highest on average in green (53.26) and white (52.80) clays. 4
Two French green clays, different arsenic. The antibacterial French green clay held 43.3 ppm arsenic; the non-antibacterial twin held 5.5 ppm (full-text table). 10
Silica sand. Cell side effects of refined montmorillonite were linked to silica sand and excess amounts. 7
| Body | Action | Date |
|---|---|---|
| US FDA (United States) | Cosmetic products and ingredients (except colour additives) do not need premarket approval; FDA can take enforcement action against non-compliant products on the market. source | 2025-11-18 |
| EFSA FEEDAP Panel (European Union) | For a montmorillonite-illite mixed-layer clay used as animal feed additive: sensitiser for skin and respiratory tract; user exposure by any route should be minimised. source | 2026-08-06 |
| NCCIH (US National Institutes of Health) (United States) | Says a 2015 review found no compelling research that detox diets remove toxins. source | 2025-03 |
When to get medical help
- Collapse, a seizure, trouble breathing or being impossible to wake after swallowing or breathing in clay or clay dust: call emergency services (911 in the US) now.
- Swallowed a clay product and feel unwell, or a child has swallowed it: call poison control (US 1-800-222-1222) or your local emergency number.
- A skin ulcer or wound with spreading redness, pus, fever or pain that is getting worse: get medical care, do not use clay instead.
- Wheeze, cough or chest tightness after breathing in dry powder: stop and get medical advice.
Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.
General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.
Frequently asked questions
What is French green clay?
Does French green clay detox the body?
Is French green clay safe to swallow?
The sources read do not support swallowing it. Reviews say large amounts of eaten clay can block iron, zinc and potassium, and that the safety of clay eating is not established. Green clays have held arsenic, lead and mercury. If someone swallowed it and feels unwell, call poison control (US 1-800-222-1222).
Does a French green clay mask help oily skin or acne?
No study of a French green clay mask was found. One 75-person study of a different branded clay mask reported less oil and fewer acne signs, but its abstract describes no comparison group and it comes from the maker's staff. Seller claims are not evidence.
Is French green clay antibacterial?
Can I put it on a wound or ulcer?
Does French green clay contain heavy metals?
Is it safe in pregnancy, while breastfeeding or for children?
Can it affect my medicines?
No interaction study was found. In theory clay can bind other substances if swallowed, so ask a pharmacist before taking clay if you use medicines.
Is breathing the dry powder a problem?
It is wise to avoid it. EFSA's 2026 opinion on a related illite-smectite clay in animal feed says it should be treated as a skin and respiratory sensitiser and exposure should be minimised.
Why do two green clays act so differently?
Is clay regulated like a medicine?
Not as a cosmetic. The FDA says cosmetic products and ingredients, except colour additives, do not need premarket approval, though it can act against non-compliant products. Other countries were not checked.
Explore by health goal
Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against PubMed records.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-25
- Last substantive update
- 2026-10-25
- How we research
- We searched PubMed, read the abstract of each cited paper, read the 2010 healing-clay review in full text on PubMed Central, and read the FDA cosmetics, NCCIH detox and Poison Control pages. Certainty ratings are the compiler's own reading. One study is from a mask maker's staff and is flagged. Regulators outside the US and EFSA beyond one abstract were not checked. No study is cited that we could not verify.
- How we rate evidence
- See "How we rate evidence" in the Evidence tab.
- Independence
- No product is promoted on this page. No affiliate links are shown.
Sources 15
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
- Adusumilli S, Haydel SE. In vitro antibacterial activity and in vivo efficacy of hydrated clays on Mycobacterium ulcerans growth. BMC Complementary and Alternative Medicine. 2016. PMID 26833071. DOI 10.1186/s12906-016-1020-5. (abstract)
- Bonglaisin JN, Kunsoan NB, Bonny P, et al. Geophagia: Benefits and potential toxicity to human - A review. Frontiers in Public Health. 2022. PMID 35958861. DOI 10.3389/fpubh.2022.893831. (abstract)
- EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), et al. Assessment of a feed additive consisting of montmorillonite-illite mixed layer clay mineral (1g557) for all animal species for the renewal of its authorisation (FIM Biotech GmbH). EFSA Journal. 2026. PMID 42564637. DOI 10.2903/j.efsa.2026.10244. (abstract)
- Fischer A, Brodziak-Dopierała B, Jańska W, et al. Analysis of Mercury Concentration in Cosmetic Clays. Toxics. 2025. PMID 40559980. DOI 10.3390/toxics13060507. (abstract)
- Gomes CSF. Healing and edible clays: a review of basic concepts, benefits and risks. Environmental Geochemistry and Health. 2018. PMID 28150053. DOI 10.1007/s10653-016-9903-4. (abstract)
- Incledion A, Boseley M, Moses RL, et al. A New Look at the Purported Health Benefits of Commercial and Natural Clays. Biomolecules. 2021. PMID 33466399. DOI 10.3390/biom11010058. (abstract)
- Wang Z, Jiang Y, Tian G, et al. Toxicological Evaluation toward Refined Montmorillonite with Human Colon Associated Cells and Human Skin Associated Cells. Journal of Functional Biomaterials. 2024. PMID 38535268. DOI 10.3390/jfb15030075. (abstract)
- Whiteside TE, Qu W, DeVito MJ, et al. Elevated Arsenic and Lead Concentrations in Natural Healing Clay Applied Topically as a Treatment for Ulcerative Dermatitis in Mice. Journal of the American Association for Laboratory Animal Science. 2020. PMID 32059757. DOI 10.30802/AALAS-JAALAS-19-000068. (abstract)
- Williams LB, Haydel SE, Giese RF, Eberl DD. Chemical and mineralogical characteristics of French green clays used for healing. Clays and Clay Minerals. 2008. PMID 19079803. DOI 10.1346/CCMN.2008.0560405. (abstract)
- Williams LB, Haydel SE. Evaluation of the medicinal use of clay minerals as antibacterial agents. International Geology Review. 2010. PMID 20640226. DOI 10.1080/00206811003679737. (full-text)
- Williams LB, Metge DW, Eberl DD, et al. What makes a natural clay antibacterial?. Environmental Science and Technology. 2011. PMID 21413758. DOI 10.1021/es1040688. (abstract)
- Zhang X, Zhang Z, Tao H, et al. Comprehensive assessment of the efficacy and safety of a clay mask in oily and acne skin. Skin Research and Technology. 2023. PMID 38009030. DOI 10.1111/srt.13513. (abstract)
- n/a. NCCIH (NIH): Detoxes and Cleanses: What You Need To Know (last updated March 2025). n/a. 2025. (full-text)
- n/a. FDA: FDA Authority Over Cosmetics: How Cosmetics Are Not FDA-Approved, but Are FDA-Regulated (content current as of 11/18/2025). n/a. 2025. (full-text)
- n/a. Poison Control (National Capital Poison Center): home page, read 2026-10-25. n/a. 2026. (full-text)
