Benzoyl peroxide is a stalwart acne treatment for many years. But is it safe? There’s been some recent studies calling this into question.
Let’s take a trip in the time machine back to my days in college chemistry lab. We used pure benzoyl peroxide as a free radical initiator for plastics polymerization. Huh? The point here is that it makes free radicals, which are, by nature somewhat destructive (in lab you needed to portion the benzoyl peroxide with a paper spatula because if it contacted a static electric charge – like if you used a metal spatula – you risked literally blowing up the lab!). This inflammatory response is helpful in causing the acne-related bacteria to “explode” on their own.
So what’s the problem? Benzoyl peroxide (as I’ve already suggested) is pretty unstable. When benzoyl peroxide degrades, it ends up, at least in part, as benzene, a highly toxic, carcinogenic compound. Recent testing suggests that’s exactly what’s happening to several acne products (800 times higher levels than the FDA says is ok).
What we don’t know is what does this really mean in terms of outcomes. Says, it’s concentrated, but how much is really getting to the patient? Benzene is volatile, so when you open the tube, it leaks into the air – is the problem inhalation (there is some risk there)? Is the amount you’re using for acne enough to actually make a difference? Is it a consequence of persistent exposure (do you need to use it for years)? Lots of questions, not many answers.
Bottom line for me is if there are no alternatives, it’s hard to believe that benzoyl peroxide is going to substantially increase your risks compared to all the other terrible stuff we’re being exposed to everyday already.
Benzoyl Peroxide in Acne Products: Debates, Uncertainty Over Safety
Nine days after the independent laboratory Valisure petitioned the US Food and Drug Administration (FDA) to recall acne products with benzoyl peroxide (BP) because of the lab's findings of extremely high levels of the carcinogen benzene, it published another report in Environmental Health Perspectives (EHP) on March 14, also warning about BP acne products.
The bottom line was the same: The laboratory, based in New Haven, Connecticut, said its analyses raise substantial concerns about the safety of BP-containing acne products currently on the market.
The lab's results showed that the products can form over 800 times the conditionally restricted FDA concentration limit of 2 parts per million (ppm) of benzene, with both prescription and over-the-counter products affected.
"This is a problem of degradation, not contamination," David Light, CEO and founder of Valisure, said in a telephone interview. BP can decompose into benzene, and exposure to benzene has been linked with a higher risk for leukemia and other blood cancers, according to the American Cancer Society.
In the wake of the findings, however, debate has erupted over the method and approach used by Valisure to test these products, with critics and companies contending that more "real-world" use data are needed. And the US Pharmacopeia (USP) is asking for full transparency about the testing methods.
In a March 8 statement, USP said the petition indicated that modified USP methods were used in the study, noting that "if changes are made to a USP method, complete validation data is necessary to demonstrate that a product meets USP standards."
However, Valisure contended that drug products need to demonstrate stability over the entire life cycle, from shipment to continued use, emphasizing that constitutes the best "real-world" approach. It also defended the methodology it used.
The reports have led to a state of uncertainty about the use of BP products.
"Right now, we have more unknowns than anything else," John Barbieri, MD, MBA, assistant professor of dermatology at Harvard Medical School and director of the Advanced Acne Therapeutics Clinic at Brigham and Women's Hospital, Boston, Massachusetts, said in a video posted on X and YouTube, summarizing the findings released by Valisure on March 6 and 14. He was not involved in the Valisure research.
In a telephone interview, Barbieri said the report "needs to be taken seriously," but he also believed the Valisure report is lacking information about testing under "real-world" conditions. He is calling for more information and more transparency about the data. What's clear, Barbieri told Medscape Medical News, is that the findings about high benzene levels are not a manufacturing error. "It's something to do with the molecule itself."
Valisure's Analyses
Valisure performed an initial analysis, using a method called gas chromatography-mass spectrometry, which is the FDA-preferred method for detecting benzene, Light said. It tested 175 acne products, 99 containing BP and 76 with other ingredients, such as salicylic acid. All the products without BP had no detectable benzene or values below 2 ppm, the FDA concentration limit for benzene.
Of the 99 BP products, 94 contained benzene without any elevated temperature incubation, according to Valisure. Using 50 °C (122 °F, the accepted pharmaceutical stability testing temperature) on 66 products, Valisure detected over 1500 ppm of benzene in two products, over 100 ppm in 17 products, and over 10 ppm in 42 products over an 18-day period.
The analysis confirmed, Valisure said in a press release and the petition, that a substantial amount of benzene can form in a BP product and leak outside the packaging into surrounding air.
The EHP paper, which includes authors from Valisure, reported that researchers took single lots of seven branded BP products, namely, Equate Beauty 2.5% BP cleansers, Neutrogena 10% BP cleanser, CVS Health 10% BP face wash, Walgreens 10% BP cream, Clean & Clear 10% cleanser, Equate Beauty 10% BP acne wash, and Proactiv 2.5% BP cleanser.
Using testing that involved gas chromatography-mass spectrometry, benzene was detected in all the BP products samples tested, and levels increased during incubation at body and shelf-life performance temperatures to more than 2 ppm. The authors concluded that the study "raises substantial concerns" about the safety of BP products currently on the market.
Methodology Debates
Two days after Valisure released its analysis on March 6, the USP reviewed the citizen's petition filed by Valisure and called for more transparency around the testing methods.
"The petition referenced USP and indicated that modified USP methods and procedures were used in the study. The presence of unsafe levels of benzene should be taken seriously," the statement said. The USP statement also noted that the Valisure analysis used modified USP methods and said that "if changes are made to a USP method, complete validation data is necessary to demonstrate that a product meets USP standards."
In its statement, USP took issue with a practice known as accelerated thermal degradation, which it said Valisure used. USP said the approach involves raising the storage temperature of a product to higher than the temperature indicated on the label for the purpose of simulating degradation over a longer period. While the approach may be acceptable, USP said, the temperatures chosen may not be what is expected to happen to the products.
In response, Light of Valisure referenced guidance issued in August, 2020, from the FDA, stating that the method it used in the BP analysis can be used to detect impurities in hand sanitizers, including benzene. (In 2021, Valisure detected high levels of benzene in some hand sanitizers and asked the FDA to take action.)
Company Response
Among the companies that took issue with the report was Reckitt, which makes Clearasil, which contains BP. In a statement, the company said, in part: "The products and their ingredients are stable over the storage conditions described on their packaging which represent all reasonable and foreseeable conditions." It said the findings presented by Valisure reflect "unrealistic scenarios rather than real-world conditions."
The Personal Care Products Council, a national trade association that represents cosmetic and personal care product manufacturers, also took issue with the findings and the approach used to evaluate the products.
FDA and the Citizen's Petition
The FDA accepted the petition, Light said, and gave it a docket number. "We'll hopefully hear more soon" because the FDA is required to respond to a citizen's petition within 180 days, he said.
"We generally don't comment on pending citizens' petitions," an FDA spokesperson said in an email. "When we respond, we will respond directly to the petitioner and post the response in the designated agency public docket."
Valisure's Patent Application
Light and others have applied for a patent on methods of producing shelf-stable formulations to prevent degradation of BP to benzene.
"We saw the problem long before we had any sort of application," Light said. The issue has been "known for decades."
Role of BP Products for Acne
In the midst of uncertainty, "the first discussion is, do we want to use it?" Barbieri said in the interview. Some patients may want to avoid it altogether, until more data are available, including more verification of the findings, while others may be comfortable accepting the potential risk, he said.
"Benzoyl peroxide is one of our foundational acne treatments," Barbieri said. In the American Academy of Dermatology updated guidelines on acne, published in January, 2024, strong recommendations were made for BP products, as well as topical retinoids, topical antibiotics, and oral doxycycline.
"When you take away BP, there's no substitute for it," Barbieri said. And if patients don't get improvement with topicals, oral medications might be needed, and "these all have their own risks."
In the Interim
Until more information is available, Barbieri is advising patients not to store the products at high temperatures or for a long time. Don't keep the products past their expiration date, and perhaps keep products for a shorter time, "something like a month," he said.
Those living in a hot climate might consider storing the products in the refrigerator, he said.
"We need more data from Valisure, from other groups that confirm their findings, and we need to hear from the FDA," Barbieri said. "There's a lot of uncertainty right now. But it's important not to overreact."