At a glance
| Chemical family | A phenylpropene (allylbenzene), a close structural relative of safrole and estragole; used as both a fragrance and a flavouring |
| CAS number | 93-15-2 |
| Classification | IARC Group 2B — possibly carcinogenic to humans (Vol. 101, 2013), on sufficient evidence in animals with no human data. NTP: clear evidence of carcinogenic activity in rats and mice. Restricted in EU cosmetics (Annex III) |
| Where you encounter it | Fragrance in perfumes (0.3–0.8%), creams and lotions (0.01–0.05%), and soaps and detergents (0.02–0.2%); essential oils for aromatherapy and massage; naturally in basil, tarragon, nutmeg and cloves; a food flavouring |
| Sleep micro-environment relevance | A fragrance in the soaps and detergents that wash your bedding, so it can persist on the fabric at the breathing zone; also inhaled from scented products and essential-oil diffusers |
| Activated carbon capture | Partly — as a semi-volatile fragrance it can be captured from air, but the cleaner lever is fragrance-free laundry and wash products, and caution with essential-oil diffusion |
What it is
Methyleugenol is a phenylpropene, structurally close to safrole (a known carcinogen) and estragole. It occurs naturally in basil, tarragon, nutmeg and cloves and in many essential oils, and it is deliberately added as a fragrance to perfumes, toiletries, soaps and detergents, and as a flavouring to foods. Regulatory — IARC Monograph Vol. 101
The reason it is on this Atlas: IARC classifies methyleugenol as Group 2B, possibly carcinogenic to humans, on the basis of sufficient evidence in experimental animals. Regulatory — IARC Monograph Vol. 101 The honest caveat belongs in the same breath: no human cancer data were available to the Working Group at all. This is an animal-evidence classification, not a demonstrated human cancer risk, and anyone telling you otherwise is overreaching. Regulatory — IARC Monograph Vol. 101
How it relates to the bedroom
It is in your laundry and your soap
This is the part most people do not know. IARC records methyleugenol as a fragrance in perfumes at 0.3–0.8%, in creams and lotions at 0.01–0.05%, and in soaps and detergents at 0.02–0.2%. Regulatory — IARC Monograph Vol. 101 Laundry fragrance is engineered to persist on fabric, so a detergent-borne fragrance reaches the sheets you spend a third of your life pressed against. Inferred — from methyleugenol's documented detergent and soap use and the designed persistence of laundry fragrance on fabric; methyleugenol specifically has not been measured on laundered bedding
Strong animal evidence, absent human evidence
The US National Toxicology Program ran two-year gavage studies and found clear evidence of carcinogenic activity in male and female rats (liver neoplasms, neuroendocrine tumours of the glandular stomach, kidney tumours and malignant mesothelioma) and clear evidence in male and female mice (liver neoplasms including hepatoblastoma). Regulatory — NTP TR-491 IARC judged that a mutational mechanism, involving DNA adducts, underlies these tumours. Regulatory — IARC Monograph Vol. 101
And yet the classification stops at 2B rather than going higher, for one reason: there is no human cancer data. None was available to the Working Group. Regulatory — IARC Monograph Vol. 101 That gap is the whole reason for the word "possibly," and it is why we will not tell you methyleugenol causes cancer in people. What we can say is that a compound with this animal record is worth not marinating your pillowcase in. Inferred — an ALARA judgement from the animal carcinogenicity plus the avoidable, continuous nature of the laundry-fragrance route
The EU restricted it
Regulators acted on the animal evidence. Commission Regulation (EU) 2017/1410 amended the Cosmetics Regulation to restrict methyleugenol in cosmetic products under Annex III. Regulatory — EU 2017/1410 What it cannot do is remove the compound from basil, tarragon and nutmeg, where it occurs naturally, so a dietary route remains regardless of what you wash your sheets in. Regulatory — IARC Monograph Vol. 101
What the research says
- IARC Group 2B — possibly carcinogenic to humans. Sufficient evidence in animals; Vol. 101 (2013). Regulatory — IARC Vol. 101
- NTP: clear evidence of carcinogenic activity in rats and mice. Liver tumours in both species; stomach and kidney tumours in rats. Regulatory — NTP TR-491
- No human cancer data exist. None was available to the IARC Working Group; this is why it is "possibly," not "probably." Regulatory — IARC Vol. 101
- A fragrance in soaps and detergents at 0.02–0.2%. Also perfumes (0.3–0.8%) and creams/lotions (0.01–0.05%). Regulatory — IARC Vol. 101
- Restricted in EU cosmetics. Annex III, via Commission Regulation (EU) 2017/1410. Regulatory — EU 2017/1410
What helps reduce it
Use fragrance-free detergent and soap for bedding. This is the avoidable, continuous exposure, and it is the one you actually control. Inferred
Go easy on essential-oil diffusers in the bedroom. Methyleugenol is a natural constituent of several essential oils used for aromatherapy and massage. Regulatory — IARC Vol. 101
Let the EU restriction work. Cosmetic products sold into the EU are limited under Annex III. Regulatory — EU 2017/1410
What does NOT help
- Panicking about basil and nutmeg. Methyleugenol occurs naturally in ordinary herbs and spices; you cannot eliminate it, and the classification rests on animal data, not human. Regulatory — IARC Vol. 101
- Calling it a proven human carcinogen. It is "possibly" carcinogenic (Group 2B). No human cancer data exist. Regulatory — IARC Vol. 101
Open research questions
- How much methyleugenol actually persists on laundered bedding from detergent fragrance, and how that compares with the dietary route — not measured. Speculation
- Whether any human cancer data will ever emerge; none existed at the time of the IARC evaluation. Speculation
Citations
- IARC Monographs Vol. 101, Some Chemicals Present in Industrial and Consumer Products, Food and Drinking-Water (2013). Methyleugenol (CAS 93-15-2) evaluated as Group 2B — possibly carcinogenic to humans, on sufficient evidence in experimental animals; no human cancer data were available. Records fragrance use at 0.3–0.8% (perfumes), 0.01–0.05% (creams/lotions) and 0.02–0.2% (soaps/detergents). NCBI Bookshelf Regulatory
- National Toxicology Program (2000). NTP Toxicology and Carcinogenesis Studies of Methyleugenol (CAS No. 93-15-2) in F344/N Rats and B6C3F1 Mice (Gavage Studies). NTP Tech Rep Ser 491:1–412. Clear evidence of carcinogenic activity in male and female rats (liver neoplasms, neuroendocrine tumours of the glandular stomach, kidney neoplasms, malignant mesothelioma) and in male and female mice (liver neoplasms including hepatoblastoma). PMID 12563349. PubMed Regulatory
- Commission Regulation (EU) 2017/1410 amending Annexes II and III to Regulation (EC) No 1223/2009 (Cosmetics Regulation). Methyleugenol restricted in cosmetic products under Annex III. EUR-Lex Regulatory
Frequently asked questions
What is methyleugenol?
Methyleugenol is a phenylpropene, a close structural relative of safrole and estragole. It occurs naturally in basil, tarragon, nutmeg and cloves and in many essential oils, and it is added as a fragrance to perfumes, toiletries, soaps and detergents, and as a flavouring to foods. IARC records its fragrance use at 0.3–0.8% in perfumes, 0.01–0.05% in creams and lotions, and 0.02–0.2% in soaps and detergents.
Is methyleugenol a carcinogen?
IARC classifies methyleugenol as Group 2B, possibly carcinogenic to humans. That rests on sufficient evidence in experimental animals: the US National Toxicology Program found clear evidence of carcinogenic activity in both rats and mice, mainly liver tumours. The honest caveat is that no human cancer data were available to the IARC Working Group at all. So it is an animal-evidence classification, not a demonstrated human cancer risk.
How does methyleugenol get into my bedroom?
Mainly through fragrance. IARC records methyleugenol in soaps and detergents at 0.02–0.2%, and laundry fragrance is engineered to persist on fabric, so it can reach the bedding you sleep against. It is also in perfumes, creams and lotions, and in essential oils used for aromatherapy and massage. Separately, there is a real dietary route through basil, tarragon, nutmeg and cloves.
Should I be worried about it?
Calibrate carefully. The animal carcinogenicity is genuinely strong and the EU restricted it in cosmetics for that reason. But there is no human cancer data, and methyleugenol occurs naturally in ordinary foods like basil and nutmeg, so it cannot be eliminated. The proportionate step is to reduce the avoidable, continuous exposure — fragranced detergent and soap on the bedding you breathe against for eight hours — rather than to fear basil.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-14. If you find a factual error, contact us.