This second study is different from the first in that it has been published in a peer-reviewed journal. “Peer reviewed journals accept studies that have been reviewed by ‘peers,’ aka experts in their fields for conflicts of interest, quality, and accuracy… [they] would review the paper and the findings to ensure certain criteria are met so that readers of the paper can trust the findings, and if it passes the criteria for credibility then it gets published,” explains Caren Campbell, MD, a board-certified dermatologist in San Francisco.
This new study also looked at almost twice as many products as the first, which studied 66 products containing benzoyl peroxide. Valisure has conducted other tests looking at benzene contamination in acne treatments, including one small study, published in the journal Environmental Health Perspectives, that found benzene in benzoyl peroxide products, and another that did not find benzene in salicylic acid acne treatments or ones with adapalene.
Another difference between the two studies is the way the benzoyl peroxide treatments were tested. In this newest study, the products remained at room temperature. In the first study, they were heated—reaching temperatures your own products would arguably never hit under normal bathroom medicine cabinet conditions. Critics of that study said those temperature increases could have coaxed benzene to form inside the products, which just wouldn’t happen in your own bathroom. “No one is going to store their anti-acne products in a car that is going to get to 70 degrees Celsius for weeks on end,” cosmetic chemist Perry Romanowski told Allure after reviewing the first study.
One reason why temperature may play a role is that, in acne products, “the benzene [may be] coming from decomposition of the active ingredient benzoyl peroxide,” cosmetic chemist Kelly Dobos explained after the first study came out. The tests suggested that subjecting some benzoyl peroxide-containing acne products to increased temperatures—between 99 and 150 degrees Fahrenheit (an approximation to the temperature of a hot car)—might accelerate that reaction, Dobos explains. The first study also found that benzene may be present in the air around the products, not just in them.
But here’s where the plot thickens—Valisure’s latest study isn’t the only follow up to their first. After their initial research came out in the spring, “two new studies were published earlier this year in response to Valisure’s work that were reassuring in the safety of benzoyl peroxide products,” explains Dobos. “One looked at benzene levels in the blood of benzoyl peroxide users compared to non users, and another examined a cohort of over 50,000 individuals for risk of cancer. The first study found no detectable differences in benzene in the blood between the groups, and the second did not find heightened cancer risk for users of BPO.” Both studies were published in the Journal of the American Academy of Dermatology, and each suggests that, in practice, benzoyl peroxide is still safe to use. “Of course, further studies are needed to strengthen these conclusions, but the information is encouraging for the safe use of BPO,” says Dobos.
