BHA (butylated hydroxyanisole) causes cancer in laboratory animals, but there is no direct evidence it causes cancer in humans at the levels found in food. The International Agency for Research on Cancer classifies BHA as a Group 2B substance, meaning it is “possibly carcinogenic to humans.” The U.S. National Toxicology Program goes slightly further, listing it as “reasonably anticipated to be a human carcinogen.” These classifications have kept BHA in a gray zone for decades, and in February 2026, the FDA launched a formal reassessment of whether BHA should remain in the food supply.
What the Animal Studies Show
The cancer concern with BHA comes almost entirely from animal research. When rats, mice, and hamsters were fed BHA in their diets, they developed both benign and malignant tumors in the forestomach, a part of the digestive tract that exists in rodents but not in humans. Male hamsters developed tumors after just 24 weeks of dietary BHA exposure. In a separate study, larval fish exposed to BHA developed liver cancer as adults.
The tumors in rodents were specifically papillomas (benign growths) and squamous cell carcinomas (malignant tumors). BHA also acted as a promoter in two-stage cancer experiments, meaning it accelerated cancer development in the forestomach and urinary bladder after those tissues had already been exposed to a cancer-initiating substance. Interestingly, it appeared to inhibit liver cancer development in rats, highlighting the complicated and sometimes contradictory behavior of this chemical in different tissues.
Why Human Risk Is Uncertain
The central debate over BHA comes down to one anatomical fact: humans don’t have a forestomach. Rodents have a forestomach lined with squamous cells that sits before the glandular stomach (the part humans do have). Research into the mechanism of BHA’s carcinogenicity found that the forestomach accumulated 14 times more of BHA’s reactive byproducts than the glandular stomach and 12 times more than the liver. This extreme local concentration of toxic metabolites in a tissue humans lack makes it genuinely difficult to translate the animal findings to people.
The mechanism itself involves BHA breaking down into reactive compounds called quinones, which deplete protective molecules in cells and can damage proteins and DNA. These reactions appear to require a threshold dose before they overwhelm the tissue’s defenses, which is one reason regulators have maintained that low dietary levels may be safe.
The largest human study on the topic, the Netherlands Cohort Study, tracked over 120,000 men and women for more than six years. Among 192 stomach cancer cases identified, researchers found no significant association between BHA intake and stomach cancer risk. If anything, the data trended in the opposite direction: those with higher BHA intake had a slightly lower (though statistically insignificant) rate of stomach cancer compared to those with the lowest intake. This single study doesn’t prove BHA is safe, but it’s the best human evidence available, and it found no signal of harm at typical dietary levels.
How Much BHA Is in Your Food
The FDA permits BHA in a range of processed foods at strictly limited concentrations. Dry breakfast cereals, dehydrated potato shreds, and potato flakes can contain up to 50 parts per million. Active dry yeast is allowed up to 1,000 parts per million. Prepared beverages and desserts made from dry mixes are capped at just 2 parts per million. These levels are tiny fractions of what caused tumors in animal studies.
The European Food Safety Authority set an acceptable daily intake of 1 milligram per kilogram of body weight. For a 150-pound person, that translates to roughly 68 milligrams per day. Average dietary intake in the Netherlands Cohort Study was about 105 micrograms per day, which is more than 600 times below that European safety limit. Most people eating a typical Western diet consume BHA well within established safety thresholds.
BHA in Cosmetics and Other Products
BHA also shows up in cosmetics, skin care products, and lip balms, where it works the same way it does in food: preventing oils and fats from going rancid. A survey of cosmetic products found BHA in about 1.6% of items tested, often appearing in shampoos and lip balms. The Cosmetic Ingredient Review Expert Panel capped BHA at 0.5% concentration in cosmetic formulations because of its uncertain toxicological profile and potential to irritate skin and mucous membranes.
California’s Proposition 65 Warning
If you’ve seen a cancer warning on a product containing BHA, it likely traces back to California’s Proposition 65. BHA was added to the state’s list of known carcinogens in 1990, based on the IARC classification. California set a “no significant risk level” of 4,000 micrograms (4 milligrams) per day. Products exposing consumers to more than that amount require a warning label. This threshold is well above what most people consume through food, which is why you’ll see Prop 65 warnings on some products but not others.
How BHA Compares to BHT
BHT (butylated hydroxytoluene) is a closely related preservative that often appears alongside BHA on ingredient labels. Their cancer profiles differ meaningfully. BHT was not found to be carcinogenic in rats or mice in standard feeding studies, though it may promote thyroid and bladder tumors under certain experimental conditions. Unlike BHA, BHT does not cause forestomach tumors. Neither substance showed a significant association with stomach cancer in the Netherlands Cohort Study. BHT is not classified as a possible human carcinogen by IARC or listed by the National Toxicology Program.
The FDA’s 2026 Reassessment
After decades of allowing BHA under rules established when it was first approved, the FDA announced in February 2026 that it would conduct a comprehensive reassessment of BHA’s safety in food. The review will evaluate whether BHA meets current scientific standards for its approved uses. The agency issued a public request for information on BHA’s use and safety data, signaling that the regulatory status quo may change. BHA had already been flagged as a top priority for review during a 2025 public comment period on the FDA’s process for reassessing food chemicals.
The outcome of this review could range from reaffirming BHA’s safety at current levels to restricting or removing it from the food supply. Several major food manufacturers have already voluntarily reformulated products to remove BHA in recent years, replacing it with alternatives like tocopherols (forms of vitamin E) and rosemary extract.