Why Benzoyl Peroxide Can Make Its Own Benzene in a Hot Car
Unlike sunscreen, benzoyl peroxide can chemically generate benzene when it gets hot, which turns the 2025 testing story into a lesson about where you keep your skincare.
Unlike sunscreen benzene, which is generally a raw-material contaminant, benzoyl peroxide can chemically degrade into benzene under heat; Valisure reported benzene formation when products were incubated at body temperature (37°C), 50°C, and hot-car temperature (70°C / 158°F), the science underpinning the FDA's 2025 testing.
The American Academy of Dermatology explains that benzoyl peroxide can break down into benzene under heat, and Medscape's coverage of the FDA's 2025 testing notes that most products tested still had low benzene levels, suggesting storage conditions are a key variable.
Questions we get a lot
Why does benzoyl peroxide form benzene but sunscreen usually doesn't?
The American Academy of Dermatology explains that benzoyl peroxide can chemically degrade into benzene, especially under heat, which is different from sunscreen, where benzene is typically a raw-material contaminant. That distinction is why storage temperature matters so much for acne products. It also explains why the 2025 testing focused on heat conditions.
At what temperature does benzene start forming?
Valisure reported benzene formation when benzoyl peroxide products were incubated at body temperature (37°C), 50°C, and hot-car temperature (70°C, about 158°F). Higher heat drove more formation, which is why a hot car or steamy bathroom is a concern. This testing helped motivate the FDA's 2025 investigation.
Does this mean my benzoyl peroxide is unsafe?
Not necessarily. Medscape's coverage of the FDA's 2025 testing found that most benzoyl peroxide products had low benzene levels, suggesting normal storage keeps the risk small. The practical takeaway is to store these products cool and avoid leaving them in hot cars. Follow any official recall guidance for specific affected lots.
r/SkincareAddiction: 'I left my benzoyl peroxide cream in my car over a heat wave, is it now basically a benzene factory or am I overthinking this?'