Benzoyl peroxide itself is not classified as a carcinogen, and decades of use in acne treatment have not produced evidence linking it to cancer in humans. The concern you’ve likely seen in headlines is slightly different: under certain conditions, benzoyl peroxide can break down into benzene, which is a known carcinogen. That distinction matters, and the details are more reassuring than the headlines suggest.
What the Cancer Classifications Say
The International Agency for Research on Cancer (IARC) places benzoyl peroxide in Group 3, meaning it is “not classifiable as to its carcinogenicity to humans.” That’s the category reserved for substances where available evidence simply doesn’t support a cancer link. It has held that classification since 1999. The FDA, for its part, has approved benzoyl peroxide as an over-the-counter acne treatment for decades and has not added cancer warnings to its labeling.
Early animal studies did raise a question about whether benzoyl peroxide could promote skin tumor growth in mice that were already exposed to a separate cancer-causing agent. A European safety committee initially flagged this concern in the late 1980s. But follow-up research found that these rodent findings didn’t translate to humans. The committee ultimately concluded that benzoyl peroxide in acne products poses no human health concerns above accepted safety standards, and no tumor-promotion warnings were warranted.
A 2025 multicenter retrospective study published in the Journal of the American Academy of Dermatology looked specifically at whether people who used benzoyl peroxide acne treatments had higher rates of benzene-related cancers, including leukemia, myelodysplastic syndrome, and non-Hodgkin lymphoma. The study found no significant association.
The Benzene Breakdown Problem
Here’s where the real concern lies. Benzoyl peroxide is a crystalline powder that, when exposed to high temperatures, can thermally decompose. During that breakdown, carbon dioxide is released and unstable molecular fragments form. Depending on the chemical environment, those fragments can recombine into several byproducts, one of which is benzene. Benzene is a confirmed human carcinogen linked to blood cancers with long-term, high-level exposure.
In 2024, a third-party laboratory submitted testing results to the FDA claiming that some benzoyl peroxide acne products contained elevated benzene levels. This triggered widespread media coverage and understandable alarm. The FDA, however, cautioned that unvalidated testing methods used by outside labs can produce inaccurate results and lead to consumer confusion. So the agency ran its own independent analysis.
What the FDA Actually Found
In March 2025, the FDA published results from its testing of 95 benzoyl peroxide acne products. More than 90% had undetectable or extremely low levels of benzene. Only a small number of products showed elevated contamination, and those were voluntarily recalled at the retail level. The recalled products included Zapzyt Acne Treatment Gel and a handful of others.
Notably, these recalls were directed at retailers, not consumers. The FDA did not instruct people to throw away products they already had at home. The agency stated plainly that “even with daily use of these products for decades, the risk of a person developing cancer because of exposure to benzene found in these products is very low.”
The FDA’s safety threshold is 2 parts per million of benzene for products used at doses of 10 grams per day or less, which translates to no more than 20 micrograms of benzene exposure daily. Manufacturers are required to test their products and ensure they fall below this limit before releasing them.
How Storage Affects Safety
Temperature is the key variable. Benzoyl peroxide is thermally stable under normal conditions, but extreme heat accelerates its breakdown into benzene. Leaving a tube of acne cream in a hot car, on a sunny windowsill, or in a steamy bathroom for extended periods could, in theory, increase benzene formation over time. Certain inactive ingredients in a product’s formula can also destabilize benzoyl peroxide and speed up degradation.
Storage guidelines for benzoyl peroxide products generally recommend keeping them at or below 25°C (77°F). Some combination products that pair benzoyl peroxide with other active ingredients require refrigeration before dispensing and have short expiration windows of just 10 weeks to 3 months. These tighter timelines exist specifically because the formulations are less stable.
For standard benzoyl peroxide washes and creams, practical steps to minimize any risk include:
- Store at room temperature in a cool, dry place away from direct sunlight or heat sources
- Don’t use expired products, since longer storage time means more opportunity for degradation
- Avoid leaving products in hot environments like cars, especially during summer months
How This Compares to Other Acne Treatments
The benzene degradation issue is specific to benzoyl peroxide’s chemical structure. Alternative acne ingredients like salicylic acid and adapalene (a retinoid) do not share the same decomposition pathway and do not produce benzene as a byproduct. If the benzene question concerns you enough to switch treatments, these are effective alternatives worth discussing with a dermatologist, though they work through different mechanisms and may not be a direct substitute for what benzoyl peroxide does particularly well: killing acne-causing bacteria.
That said, the practical risk from properly stored, in-date benzoyl peroxide products remains very low. The vast majority of products on shelves today test well within safety limits, and the FDA continues active surveillance of the market to ensure that stays true.