Having previously shown that irradiation of RP with UVA leads to the formation of photodecomposition products, synthesis of reactive oxygen species, and lipid peroxidation induction, Xia et al. demonstrated comparable results, identifying RP as a photosensitizer following irradiation with UVB light (Int. J. Environ. Res. Public Health 2006;3:185-90).
Recommendations
In light of the controversy swirling around RP and the appropriate concern it has engendered, in addition to the weight of evidence as well as experience from personal observation, I advise patients to avoid daytime use of products with RP high on the ingredient list. I add that it poses real risks while offering minimal benefits. Such patients should be using retinol or tretinoin. I recommend the use of retinoids at night, to avoid the photosensitizing action induced by UVA or UVB on retinoids left on the skin.
Conclusion
Retinyl palmitate does not penetrate very well into the skin. Consequently, for over-the-counter topical formulations, I recommend retinol instead. Because of the slow penetration of RP into the skin, the RP that remains on the skin will undergo photoreaction more than a substance that is rapidly absorbed. When exposed to light, RP on the skin may undergo metabolism and/or photoreaction to generate reactive oxygen species. These reactive oxygen species or free radicals can theoretically lead to increased skin cancer. That said, sufficient evidence to establish a causal link between RP and skin cancer has not been produced. Nor, I’m afraid, are there any good reasons to recommend the use of RP. More research on this subject is needed and will likely emerge in a timely fashion.
Dr. Baumann is in private practice in Miami Beach. She did not disclose any conflicts of interest. To respond to this column, or to suggest topics for future columns, write to her at dermnews@frontlinemedcom.com. This column, "Cosmeceutical Critique," appears regularly in Skin & Allergy News.