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Formaldehyde (free) vs Butylated Hydroxyanisole: which is worse?

Quick answer: Formaldehyde (free) carries the heavier risk profile. Formaldehyde (free) is banned in the EU and allowed in the US; Butylated Hydroxyanisole is in the EU and in the US.

PropertyFormaldehyde (free)Butylated Hydroxyanisole
EU statusBanned
US statusAllowed
Risk levelhigh
Banned inEuropean UnionJapan (banned for foods containing fats and oils)
Restricted inEuropean Union (restricted; banned in baby food), United Kingdom
Categorycmradditive
Where it hidesnail hardener, keratin treatment, eyelash glue

What is Formaldehyde (free)?

Formaldehyde (free) is free formaldehyde used directly as a preservative and in salon hair treatments.

What is Butylated Hydroxyanisole?

Butylated hydroxyanisole (BHA) is a synthetic phenolic antioxidant preservative derived from petroleum (see also bha entry). It is a mixture of 2-BHA and 3-BHA isomers, used to prevent oxidative rancidity in fats, oils, and fat-containing foods. Chemical formula C11H16O2.

Documented risks

Formaldehyde (free): A known human carcinogen (IARC Group 1). Banned from direct use in EU cosmetics; allowed in US products with limited oversight.

Butylated Hydroxyanisole: IARC classifies BHA as Group 2B (possible human carcinogen) based on forestomach tumor studies in rodents at high doses. The NTP lists it as 'reasonably anticipated to be a human carcinogen.' EFSA's 2012 review found endocrine-disrupting potential. Japan banned it for food use. The FDA permits it at 0.02% of fat content. Concerns about estrogen-receptor interaction have been documented in animal studies. Contact dermatitis from cosmetic use is reported.

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