Beauty ingredient · Preservative / hair smoothing
Formaldehyde
- CAS
- 50-00-0
A preservative and the active agent in some keratin hair-smoothing treatments (also called formalin or methylene glycol).
- Preservative
- Expert review pending
Concern level
Banned or revoked by a major regulator, or classified by IARC as Group 1 or 2A at relevant exposure. The concern level sets how many points formaldehyde costs on a product’s receipt.
What the evidence says
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IARC Group 1 (carcinogenic to humans)Regulatory
IARC classifies formaldehyde as Group 1 and the US National Toxicology Program lists it as a known human carcinogen, mainly from inhaled exposure. [1][2]
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Not permitted in cosmetics somewhereRegulatory
Prohibited in EU cosmetics since 2019 and in California and Washington cosmetics since 2025; it is released as a gas when hair-smoothing products are heated. [3][4][5][6]
Evidence tiers say how sure the evidence is, separately from how much it matters. About evidence tiers.
Rules around the world
| Where | Status | Details | Date | Source |
|---|---|---|---|---|
| European Union | Banned | Prohibited in cosmetic products (Annex II of Regulation (EC) No 1223/2009). Moved from the preservative list to Annex II in 2019. | Jun 12, 2019 | [3] |
| California (US) | Banned | Not allowed in cosmetics from January 1, 2025 (AB 2762), including paraformaldehyde and methylene glycol. | Jan 1, 2025 | [4] |
| Washington State (US) | Banned | Not allowed in cosmetics from January 1, 2025 (RCW 70A.560). | Jan 1, 2025 | [5] |
| Canada | Restricted | Not in aerosols; limits for oral products (0.1%), other products (0.2%) and nail hardeners (5%). | — | [7] |
| California (US) | Warning label required | Formaldehyde (gas) is listed under Proposition 65 (cancer, 1988). | Jan 1, 1988 | [8] |
“Banned” means explicitly prohibited or withdrawn after review; “not permitted” means never authorized there. We use each regulator’s own words.
Names GoodSwap recognizes on labels (8)
- formalin
- methanediol
- formaldehyde
- oxymethylene
- formic aldehyde
- methylene glycol
- paraformaldehyde
- formaldehyde solution
Sources
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Agents Classified by the IARC Monographs, Volumes 1–142 (List of Classifications)
monographs.iarc.who.int
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Report on Carcinogens, 15th Edition: Formaldehyde
“Formaldehyde is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans and supporting data on mechanisms of carcinogenesis.”
ntp.niehs.nih.gov
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“Formaldehyde should also be added to the list of substances prohibited in cosmetic products in Annex II to Regulation (EC) No 1223/2009.”
eur-lex.europa.eu
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California AB 2762 (2020), Toxic-Free Cosmetics Act (Health and Safety Code §108980)
“Commencing January 1, 2025, no person or entity shall manufacture, sell, deliver, hold, or offer for sale, in commerce any cosmetic product that contains any of the following intentionally added ingredients”
leginfo.legislature.ca.gov
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Revised Code of Washington, Chapter 70A.560 (Toxic-Free Cosmetics Act)
“(a) Ortho-phthalates; (b) Perfluoroalkyl and polyfluoroalkyl substances; (c) Formaldehyde (CAS 50-00-0) and chemicals determined by the department to release formaldehyde;”
app.leg.wa.gov
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Hair Smoothing Products That Release Formaldehyde When Heated
“These products often contain formaldehyde, also known as formalin and methylene glycol.”
fda.gov
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Cosmetic Ingredient Hotlist: prohibited and restricted ingredients
“The following ingredients are only permitted in cosmetic products under the conditions of use specified below:”
canada.ca
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Proposition 65 List of Chemicals Known to the State to Cause Cancer or Reproductive Toxicity
“The date refers to the initial appearance of the chemical on the list.”
oehha.ca.gov