BHA (Butylated Hydroxyanisole)
In plain terms
A synthetic antioxidant that keeps fats and oils from going rancid, used in both food and cosmetics. Its close relative BHT raises far less concern.
What the evidence shows
BHA is a preservative with a real carcinogen flag and an honest dispute over how much it means for people. The US National Toxicology Program has listed it since 1991, and still does, as reasonably anticipated to be a human carcinogen, based on forestomach tumors in rats, mice, and hamsters; IARC places it in its possibly-carcinogenic group. The counterargument is anatomical: humans have no forestomach, so European reviewers question how far the rodent result carries. BHA also shows weak estrogen-like and anti-androgen activity in lab studies, though the EU panel found that signal short of proof. California lists it as a carcinogen and the FDA put it under review in 2026. Given a known animal carcinogen with gentler substitutes available, the cautious call is to skip it, while being clear the human risk is not settled.
On the label
Listed as BHA or butylated hydroxyanisole, and in foods sometimes as E320. In California, products meant for the lips may carry a Proposition 65 cancer warning for it.