Newly Published Research Raises Questions About Sunscreen

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An article published in the February issue of Melanoma Research concludes that sunscreen usage needs to be reassessed and that appropriate regulatory bodies need to clarify that sunscreen products be used only for preventing sunburn.

An article published in the February issue of Melanoma Research, entitled “Sunscreen ingredients inhibit nitric oxide synthase (iNOS): a possible biochemical explanation for the sunscreen melanoma controversy,” concludes that sunscreen usage needs to be reassessed and that appropriate regulatory bodies need to clarify that sunscreen products be used only for what they do well: prevent sunburn.

Researchers at the Memphis VA Medical Center and the University of Tennessee Health Science Center (UTHSC) have reported an effect of sunscreen ingredients on the skin that might explain why sunscreens seem less effective than expected in the prevention of melanoma.

They found that several sunscreen ingredients can block the development of redness in the skin, as well as absorb some of the sun’s rays. This would allow unwary sunscreen users to inadvertently receive excessive sun exposure without the warning usually afforded by the familiar red nose and pain of sunburn.

“People should not wear sunscreen and assume they’re fully protected from melanoma,” said E. William Rosenberg, M.D., University of Tennessee Health Science Center (UTHSC) dermatology researcher, VA physician and co-author of the article with primary investigator, Thomas M. Chiang, Ph.D., Research and Development Service, Memphis VA Medical Center and adjunct professor, UTHSC College of Medicine.

According to Dr. Chiang’s laboratory experiments, the ingredients of sunscreen change the body’s natural reaction to sunlight. Dr. Rosenberg explained, “Apparently sunscreens may not prevent sunburn only by blocking sunlight; they also appear to potentially have anti-inflammatory properties. This means that people who stay in the sun for prolonged periods may not realize they’re getting overexposed because they don’t feel sunburned. It raises serious questions about the types of public health messages being sent about sunscreens.”

“These in-vitro findings are counter-intuitive because everyone assumes sunscreens are purely protective. Our results must be verified by studies in human skin,” commented John C. Dowdy, Ph.D., Rapid Precision Testing Laboratories, “but reports that some strains of melanoma cells secrete substances that also inhibit nitric oxide synthase are particularly troubling.”

The experiments for this UTHSC-supported study were conducted in Memphis at the VA Medical Center, and the findings were published in an article co-authored by Thomas M. Chiang, Ph.D., VA Medical Center; Robert M. Sayre, Ph.D. and John C. Dowdy, Ph.D., Rapid Precision Testing Laboratories; and Nathanial K. Wilkin, M.D. and E. William Rosenberg, M.D., UTHSC.