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Light Energy and Sunscreens

By: Peter T. Pugliese, MD
Posted: March 26, 2009, from the April 2009 issue of Skin Inc. magazine.

page 8 of 13

The Skin Cancer Foundation recommends applying at least 2 tablespoons of sunscreen—the same amount used in testing (2 mg/cm2 of skin)—to exposed areas 30 minutes before sun exposure, and reapplying it every two hours or immediately after excessive sweating or swimming. At times, if you want to increase the protection, just do a double application after the first application is dry.

Notes on tanning beds

UVA radiation makes up most of the radiation in tanning beds, which is associated with malignant melanoma, the most deadly form of skin cancer. It is fairly well established that each of the three main types of skin cancer—basal cell carcinoma, squamous cell carcinoma and melanoma—is caused by sun exposure. People who visit a tanning salon at least once a month are 55% more likely to develop melanoma than those who don’t. Those who use sun lamps to tan while in their 20s have about a 150% higher risk of skin cancer than similarly aged women who do not use tanning beds.

You know that exposure to UV radiation induces two of the most common DNA mutations known in cellular biology. Cells have developed a number of repair mechanisms to counteract the DNA damage caused by UV radiation, but they are not 100% effective. Exposure to UV radiation has a detrimental effect on the immune system, causing changes in antigen presentation by Langerhans cells and macrophages, and reducing the activities of natural killer cells and T cells. Herpes simplex is a frequently seen infection after UV exposure. UVA is clearly associated with aging changes in the skin, as well as the development of skin cancer. Most aging changes you have learned about in the skin are due to UVA rays destroying collagen and connective tissue. One good way to cause premature aging, including wrinkles, sunspots and loss of skin elasticity, is to use tanning beds.

The best of all worlds

What is new in the world of sunscreens is the use of microcapsules to encapsulate sunscreen and prevent direct contact of the sunscreen agent with the skin. This would act to markedly reduce, or even prevent sensitization from the degradation of the sunscreen. By adding a photostablilizer, the best of all worlds could be possible.