Monday, March 18, 2024

What is the rate of benzene formation from benzoyl peroxide decomposition?

In this week's C&EN, this bit of news about recent Valisure findings (article by Craig Bettenhausen):  

Concerns about benzene in personal care products are back, this time in acne medications based on benzoyl peroxide. Benzene is known to cause cancer in humans.

The independent analytical lab Valisure filed a petition last week asking the US Food and Drug Administration to recall and suspend sales of all benzoyl peroxide products. David Light, the firm’s cofounder and president, says his team found that the ingredient decomposes to benzene in consumer product formulas.

Valisure has found benzene in multiple consumer products in recent years, including hand sanitizer, sunscreen, dry shampoo, and aerosol antifungal medication. But in those cases, the benzene seems to have been a contaminant in the raw materials, and the findings were limited to certain batches and brands.

In acne products, Light says, the primary active ingredient breaks down into benzene under conditions that products might encounter in transport and in the home. The firm also found that the benzene diffused out of many of the bottles over time. “The evidence strongly shows us that this is a broad benzoyl peroxide problem,” he says. “We don’t have confidence on any product being immune at this point.”

Consumer product makers insist their acne medications are safe. Estée Lauder, which uses benzoyl peroxide in one Clinique-brand product, says it is “an FDA-approved and commonly used ingredient for acne treatment. . . . This product, like all of our products, is safe for use as intended.”

The industry’s criticism emphasizes storage conditions. Much of Valisure’s data documents the emergence of benzene over time in products held at 50 °C and 70 °C—temperatures that consumers are told to avoid. The label on the acne product Clearasil, for example, instructs consumers to store the product at room temperature away from bright light. And some prescription-strength benzoyl peroxide formulas are meant to be stored in the fridge.

I'm not an analytical chemist, so I have no idea whether or not their findings are correct. I am a (former) organic chemist, though, and I have a gut level skepticism that solid-ish benzoic acid radicals will undergo decarboxylation as opposed to (I dunno) abstracting a hydride from some other molecule in the formulation. 

What is the literature around this? A brief Google search doesn't offer a lot of answers. If there is a raft of evidence of radical-initiated decarboxylation of benzoyl peroxide, maybe I might believe it, but I guess I'm still quite skeptical. (Don't forget that Light has patented a technology around this, so let's remember that (as always) there are conflict of interest concerns.) 


  1. That is interesting. I'm also not an analytical chemist but am wondering could the analytical method be driving this conversion as well? The methods appear to be GCMS (thermal) and SIFT-MS (ionization by microwave plasma). I don't really know anything about SIFT and nor the thermal stability of Benzoyl Peroxide. However I did find the publication from Light and I'm surprised to not see a conflict of interest statement in the web-based pub.

  2. My daughter shared a TikToc with me this weekend about cooking your acne medicine in the oven at 158°F for some amount of time. My comment to her was that I doubt you would make much if any benzene, so thanks for brining this to me attention. I looked at the Valisure website and this seems to me that they are trying to use fear to get interest in their technology to make “safer” skin care products. Sorry CJ, I do not believe in the “there is no safe level” of any chemical. As you know the dose makes the poison and I do appreciate that biological half-life of chemicals can make this a problem down the road, but we can detect many chemicals at levels never before seen and we simply do not have the data to say that it is a problem for a majority of the population.

  3. As an academic organic chemist, I was taught about reactions that take place in the lab in reaction vessels over several minutes to a few hours and I was almost exclusively taught about the major reaction products. I have had to unlearn many of those assumptions to explain reactions that I have observe during stability studies on pharmaceutical products.


looks like Blogger doesn't work with anonymous comments from Chrome browsers at the moment - works in Microsoft Edge, or from Chrome with a Blogger account - sorry! CJ 3/21/20