Essential Oil Purity and Adulteration: What Testing Studies Found
What published laboratory studies found when they tested commercial essential oils for adulteration, and what those findings can and cannot tell a buyer.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Are the essential oils sold in shops what the bottle says? The honest answer from the studies we read is: sometimes not, but no study we found measures how often across the whole market. This page summarizes what a few published analyses found. It names no brands, and these are findings about the products tested, not about any seller.
How the sources define the terms
"Adulteration" here means an oil is not what it is sold as. A 2021 analysis describes common forms: adding cheaper oils or synthetic materials, and diluting with vegetable oil. [1] NIEHS says synthetic oils are not considered true essential oils. [2] Separately, FDA says there is no regulatory definition for "essential oils" as a term. [3]
What the studies found
| Question | What the source found | Strength of evidence |
|---|---|---|
| Were "sandalwood" oils bought from shops what they said? | Six oils sold as sandalwood were compared with an international standard; none met it. Only one contained both santalols typical of Santalum album. [4] Three looked like Amyris balsamifera oil, a different plant, and two were synthetic mixtures. [4] Labels gave correct information in three of six. [4] | One small laboratory study; not a market survey |
| Were commercial lavender oils consistent? | Four lavender oils from one national market differed widely. Some had unusually high fatty acid esters and synthetic glycols, suggesting possible dilution or adulteration. [5] | Four products, one market; authors say "possible" |
| Can adulteration be found in vetiver oil? | Of eight commercial vetiver oils, NMR methods found six adulterants in four samples. [6] | Eight products; a method study |
| How well do routine tests catch vegetable oil dilution? | In a vetiver study, GC-MS did not detect adulteration with vegetable oils. [6] A separate study says absolute quantitation is needed to show dilution with heavy vegetable oils. [1] | Two method studies |
The sandalwood paper adds two cautions: it says adulteration of this kind can increase an oil's allergenic effect, and that the toxicological properties of some of the synthetic chemicals it found are unknown. [4]
How labs tell the difference
Labs compare an oil to a reference profile of genuine samples. One study built its reference from 20 genuine batches of each oil. [1] It states that adulteration can only be shown when a suitable reference profile exists. [1] Other approaches include radiocarbon methods that separate plant-derived carbon from petrochemical-derived carbon. [7] Racemic mixtures of mirror-image molecules are often a sign that a component was made in a lab. [8] See GC-MS Testing and Batch Reports Explained.
Frequently asked questions
Are most essential oils fake?
We do not know. The studies we read tested small numbers of products. Some found problems, but none we read measures how common they are. [4][5]
Why would someone adulterate an oil?
One sandalwood study says such oils are highly desired but expensive, and that counterfeits are sold in shops. [4]
Can I tell if an oil is adulterated by smell?
We found no source showing that smell reliably detects adulteration. Proper evidence not found; we searched PubMed and regulator pages.
Does a pure oil mean a safe oil?
No. Purity describes composition, not safety. Poison Control says many essential oils can cause rashes and some are poisonous if swallowed. [9]
Does adulteration matter for allergy?
One sandalwood paper says adulteration can increase the allergenic effect of an oil. [4] Ask a clinician if you have reacted to scented products.
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.
Limits and uncertainty
- The studies tested a handful of products each. We did not find a survey of how common adulteration is.
- Natural variation is real: NIEHS says an oil's composition can vary within the same plant species. [2] A reference range is therefore needed before calling a sample fake.
- "Proper evidence not found": we searched PubMed and the FDA, NIEHS, NCCIH and Poison Control pages and found no study linking a purity test result to a health outcome in people.
Safety and who should ask a clinician
Poison Control says it can be hard to know what species, concentration or contaminants are in an essential oil bottle. [9] Adulteration is one reason. If a reaction occurs, Poison Control advises stopping use and gently washing the oil off. [9] If an oil is swallowed, call Poison Help at 1-800-222-1222. [9] Ask a pharmacist or clinician about use with medicines, pregnancy or children. See also Essential Oil Quality and Labels and Product Quality and Contamination.
References
- Adulteration of Essential Oils: A Multitask Issue for Quality Control. Three Case Studies. Molecules 2021 (full text at PMC8471154). Read 2026-10-23.
- National Institute of Environmental Health Sciences (NIEHS). Essential Oils. Read 2026-10-23.
- U.S. Food and Drug Administration. Fragrances in Cosmetics. Read 2026-10-23.
- A Comparison of the Composition of Selected Commercial Sandalwood Oils with the International Standard. Molecules 2021 (full text at PMC8070282). Read 2026-10-23.
- Uncovering adulteration and quality variations in commercial lavender essential oils from the Egyptian market using GC-MS and chemometrics. Sci Rep 2026. Read 2026-10-23.
- Differential NMR and chromatography for the detection and analysis of adulteration of vetiver essential oils. Talanta 2022. Read 2026-10-23.
- Radiocarbon-based direct liquid scintillation counting method to quantify biogenic carbon and fossil-derived synthetic adulterants in commercial essential oils. Talanta 2026. Read 2026-10-23.
- Fundamental Chemistry of Essential Oils and Volatile Organic Compounds, Methods of Analysis and Authentication. Plants (Basel) 2022 (full text at PMC8955314). Read 2026-10-23.
- Poison Control (National Capital Poison Center). Essential oils: Poisonous when misused. Read 2026-10-23.