Clay Types at a Glance and How They Differ
A plain comparison of bentonite, kaolin, illite and medical smectite: what each is, what the sources we read found, and why one clay's results do not transfer to another.
Content last updated . This page has not been medically reviewed.
The short answer: clays are different minerals, and a result for one clay, product or route does not carry over to another. A mouse study found that illite, montmorillonite and kaolinite clays worked differently on infected wounds. [1] A medical smectite tested for children's diarrhea is a refined medicine, not a cosmetic clay powder. [2] This page compares the clays we have researched, and keeps seller claims, lab findings, human trials and regulatory uses apart.
What the question is
Shop labels say "healing clay", "green clay", "white clay" and "bentonite" as if they were interchangeable. They are not. Names can describe the mineral (for example montmorillonite), the place it comes from (French green) or the use (fuller's earth). We read only a few sources that compare clays side by side, so the table below says "not found" where we have no source.Clay types compared
| Clay | What it is (as far as we read) | What the sources we read found | Evidence label | Route, product and who was studied |
|---|---|---|---|---|
| Bentonite | A natural clay formed from volcanic ash, made mostly of montmorillonite. [3] | A 2024 review of lab, animal and preliminary clinical work says larger randomized trials are needed. [3] An add-on trial of a bentonite mask with a plant extract in 60 people with moderate acne reported fewer lesions than a placebo mask. [4] | Promising but limited | Skin masks and gels; see Bentonite clay |
| Montmorillonite (calcium) | A smectite clay; the main mineral in bentonite. [3] | A 2025 review calls it low-risk when properly sourced and says pharmaceutical-grade products may give consistent results. It covers many uses, from diarrhea to skin, much of it preclinical. [5] | Promising but limited | Review of many forms and products |
| Smectite or diosmectite (medical) | A refined dioctahedral smectite, used as a medicine. [2] | A 2006 meta-analysis of 9 randomized trials (1,238 children) found smectite shortened diarrhea by about 23 to 24 hours and raised the chance of cure on day 3 (risk ratio 1.64), with similar side effects. The authors said most trials had important limitations and that it may be a useful add-on to rehydration. [2] | Promising but limited | Refined medical product, swallowed, in children with acute diarrhea. Not a cosmetic clay and not a "detox" |
| Kaolin | A clay listed in an FDA skin-protectant rule at 4 to 20 percent. [6] | The FDA ingredient list shows kaolin among skin-protectant ingredients. Our Kaolin clay page covers the label wording. In mice, kaolinite was the least effective clay on infected wounds, and the group had severe dermatitis. [1] | Established for a labeled skin-drying use; lab or animal only for infection | Labeled drug products (US); mice |
| Illite | One of the natural clays tested in mice. [1] | In mice with MRSA-infected skin wounds, illite clays gave the best results of the clays tested. [1] | Lab or animal only | Wet poultice on mouse skin wounds |
| French green, rhassoul, fuller's earth, red and pink clays, Dead Sea mud, attapulgite, zeolite | Named clays and muds sold for skin and baths. | Proper evidence not found in the sources we compared for this guide. See each page: French green clay, Rhassoul clay, Fuller's earth, Red and pink clay, Dead Sea mud, Attapulgite, Zeolite | Insufficient evidence in this guide | Not applicable |
| Therapeutic mud (peloids) | Mud applied in spa or clinic treatments. | A 2026 systematic review of 28 randomized trials found less pain and better function in adults with musculoskeletal disorders, with no increase in serious adverse events. [7] | Promising but limited | Supervised mud treatment for joint and muscle problems, not a face mask |
What the table does not tell you
- Cosmetic safety is judged clay by clay. A 2026 expert panel (Cosmetic Ingredient Review) assessed eight naturally sourced clays. It judged kaolin safe at current cosmetic uses and the other seven safe at current uses, except that data were insufficient where products may be breathed in. [8] We read only the abstract, so we do not name the other seven here.
- Many "clays" are not one thing. One cosmetic study used four clays from sand-extraction residues and did not name their minerals. [9] The label "clay" alone does not tell you what is in the jar.
- Medical clay is a different product. The smectite results above come from a refined medicine for children with diarrhea. [2] They do not mean any clay powder is safe to swallow. See Poisoning: urgent help.
- Detox. For "removes toxins", Proper evidence not found in the sources we read. NCCIH's detox page found only a small number of generally low-quality human studies. See Detox claims checked.
Related pages
Frequently asked questions
Is bentonite the same as kaolin?
No. Bentonite is made mostly of montmorillonite and forms from volcanic ash. [3] Kaolin is a different clay, listed in an FDA skin-protectant rule at 4 to 20 percent. [6]
Which clay is best for skin?
We found no proper evidence to rank clays for skin. The small human studies we read were on bentonite masks, and the mouse study found different clays worked differently. [1][3][4]
Is the clay medicine for diarrhea the same as clay powder?
No. The trials were of a refined dioctahedral smectite used as a medicine in children, and the authors said most trials had important limitations. [2] Do not swallow cosmetic clay as a substitute.
Does any clay detox the body?
We found no proper evidence that it does. NCCIH found only a small number of generally low-quality human studies of detox programs, none showing toxins removed. [11]
Are clays safe for children or in pregnancy?
The sources we compared do not say. Ask a clinician, and call Poison Help if a child swallows a clay product and is unwell. [10]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety by group
- Swallowing. Do not swallow a cosmetic or garden clay because of a table like this one. If someone swallowed a clay product and is unwell, call Poison Help (US 1-800-222-1222) or use the online tool, and call 911 for collapse, seizure, trouble breathing or if the person cannot be awakened. [10]
- Skin. Patch test any new clay; see Clay face masks: safety and patch testing. Wounds are a separate question; see Clay on wounds and skin conditions.
- Breathing. The panel found data insufficient for mined clays in products that may be breathed in. [8] Avoid raising dust.
- Metals and contamination. The sources we read for this guide do not give metal levels for retail clays. See Heavy metals in natural ingredients.
- Pregnancy, breastfeeding, medicines, kidney disease, children. Not covered by the sources we compared here. Ask a clinician or pharmacist; see medication interactions.
References
- Natural and ion-exchanged illite clays reduce bacterial burden and inflammation in cutaneous meticillin-resistant Staphylococcus aureus infections in mice. J Med Microbiol. 2016;65(1):19-27. PubMed 26508716 (abstract read through Europe PMC). Mouse study. Read 2026-10-24.
- Meta-analysis: Smectite in the treatment of acute infectious diarrhoea in children. Aliment Pharmacol Ther. 2006;23(2):217-227. PubMed 16393300 (abstract read through Europe PMC). Meta-analysis of randomized trials. Read 2026-10-24.
- Zafar K, et al. The potential cutaneous benefits of bentonites and montmorillonites. Arch Dermatol Res. 2024;316(10):702. PubMed 39438324 (abstract read through Europe PMC). Review. Read 2026-10-24.
- The Therapeutic Effects of a Bentonite-Based Facial Mask With Alcea sulphurea Extract on Acne Severity and Patient Experience: Add-On Randomized Controlled Clinical Trial. J Cosmet Dermatol. 2025;24(12):e70586. PubMed 41347526 (abstract read through Europe PMC). Read 2026-10-24.
- Ng MK, et al. Human Health Applications of Calcium Montmorillonite Clay: A Systems-Based Review. Cureus. 2025;17(10). PubMed 41306171 (abstract read through Europe PMC). Narrative review. Read 2026-10-24.
- U.S. Code of Federal Regulations, Title 21, Part 347: Skin protectant drug products for over-the-counter human use. Section 347.10 ingredient list read through the eCFR data service 2026-10-24.
- Effectiveness and Safety of Mud Therapy (Pelotherapy) for Musculoskeletal Disorders: A Systematic Review and Meta-Analysis. J Lifestyle Med. 2026. PubMed 42719543 (abstract read through Europe PMC). Read 2026-10-24.
- Amended Safety Assessment of Naturally-Sourced Clays as Used in Cosmetics. Int J Toxicol. 2026;45(3_suppl):65S-107S. PubMed 42313106. Cosmetic Ingredient Review panel assessment (abstract read through Europe PMC). Read 2026-10-24.
- Physicochemical Characterization and Safety Assessment of Cosmetic Gels and Emulsions Containing Sand-Extraction Clays. J Cosmet Dermatol. 2025. PubMed 41128013 (abstract read through Europe PMC). Read 2026-10-24.
- Poison Control (America's Poison Centers). Poison Control home page. Read 2026-10-24.
- National Center for Complementary and Integrative Health (NIH). “Detoxes” and “Cleanses”: What You Need To Know. Read 2026-10-24.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.