ASK THE EXPERT: Are sunscreens safe? I have heard that their ingredients can cause cancer.

By Ronald Siegle, MD

Dr. Siegle is a dermatologic surgeon. He is clinical professor of Dermatology and Otolaryngology at The Ohio State University and in private practice in Columbus. He received his dermatology training at the University of Michigan and his surgical fellowship at Duke University. He also holds a Master’s of Science degree in Human Nutrition from Columbia University. He is the author of a surgical textbook and numerous articles.

Q: Are sunscreens safe? I have heard that their ingredients can cause cancer.

It is important to ask questions about the safety of products we use regularly, especially since some have been found to have a negative effect on our health. Fortunately, we have research scientists who work to find answers to our questions. The best, most trustworthy answers to questions about sunscreen safety are based on a review of the newest information that has been both peer-reviewed (evaluated by experts in the field) and published in respected scientific journals. The “worst” answers come from individuals or special interest groups who may have a pertinent question but whose theories are untested or, if tested, unsubstantiated by other studies. This is what some people might call “junk science,” and what some media outlets might call good stories for a slow news day! Let’s look at three of the most commonly questioned sunscreen components. 

Q. Can the UV filter oxybenzone cause cancer? 

“Junk Science” answer: An old research study on rodents suggested that oxybenzone can penetrate the skin and produce free radicals, harmful substances that, in theory, may contribute to the development of melanoma, the deadliest form of skin cancer.

Best answer: Oxybenzone underwent extensive review and was approved by the FDA for its current use in sunscreens. It has been available in the US for more than 20 years and there is no evidence that it has any serious side effects in humans. Research on human subjects provides the most relevant and useful information about the safety of substances. We can’t automatically assume that research findings on rodents are relevant in humans. 

Q. Does retinyl palmitate speed the growth of tumors after sun exposure? 

“Junk science” answer: A special interest group says an FDA study on mice done 10 years ago suggests that retinyl palmitate may speed the growth of tumors. The study was never published.  

Best answer: Retinyl palmitate is the form of vitamin A that is stored by the skin. There is no evidence that vitamin A is carcinogenic in humans. In fact, vitamin A compounds (retinoids) actually help prevent skin cancer, eliminate skin precancers, and help reverse the aging effects of sun damage. The mouse study has not been published in a peer-reviewed journal, which suggests that its findings were not deemed worthy of publication. 

Q. Are nanoparticles (tiny, or “micronized”-sized particles) in sunscreen absorbed by the skin, and are they harmful? 

“Junk science” answer: In theory, the small size of these particles could allow penetration through the skin, where the particles could gain access to DNA, causing skin cell mutations that can lead to cancer.  

Best answer: Sunscreen is applied to the top layer of skin, made up of dead cells, and multiple studies have shown that nanoparticles do not penetrate living skin. The general consensus is that they pose no risk to human health. Dermatologists know that one in three Caucasians will get skin cancer during their lifetime. Data clearly show that sunscreens help prevent skin cancer. For more information on minimizing your risk of skin cancer and sun damage, please read our Prevention Guidelines.

Published on November 15, 2011