Relationship between sunscreen and aging, skin cancer, deserves scrutiny

June 1, 2011

One of the most commonly used and most controversial products recommended by dermatologists is sunscreen. I would argue that sunscreens are also the most misunderstood and misused skincare products.

Key Points

Sunscreens were originally developed by the military to prevent heat stroke in recruits on the surface of aircraft carriers in the South Pacific.

The first sunscreen, red veterinary petrolatum, was not a good sunscreen in modern terms, but it was modestly successful in preventing sunburn-related illness.

Sunscreens were never intended to prevent sunburn. They were only intended to prolong the amount of sun exposure required to obtain sunburn. Further, sunscreens were never intended to prevent tanning. Only recently have UVA filters been developed that can prevent tanning in a meaningful manner. It is clear that patients do not understand these issues.

Aging issues

Perhaps the biggest misnomer is that sunscreens prevent aging. Most anti-aging moisturizers base their claim on listing sunscreen filters under active agents, but no one has ever proven that sunscreens prevent aging. It is an assumption based on observation.

To do such a study would be very difficult and expensive. Thousands of subjects would need to be enrolled in all geographic areas of all Fitzpatrick skin types of both sexes at birth. The group would be randomized into two subsets: One group would be given unlimited sunscreen for daily application from birth until death, and the other group would be told not to apply any sunscreen from birth until death.

Both groups would be required to keep diaries of daily sun exposure so the results could be analyzed in terms of total lifetime UV radiation dose. Skin biopsies and photographs would be taken of both groups, and an independent panel of blinded dermatopathologists would analyze the histology from both groups.

What's more, an independent panel of blinded dermatologists would analyze the photographs to determine who had younger-appearing skin. Based on the statistical analysis, the study then might be able to validate the commonly held contention that sunscreens prevent aging.

Indeed, an argument could be made that sunscreens actually encourage aging by allowing consumers to stay in the sun longer before they experience pain. This prolonged exposure would increase the total lifetime UV radiation dose, and, based on animal models, might increase the appearance of aging skin.

Sunscreens and cancer?

There also have been popular press assertions based on the medical literature that sunscreens cause skin cancer. This may be true if, indeed, sunscreen allows more lifetime sun exposure, but the study outlined above still needs to be performed. Problems arise when we take the intended purpose of sunscreens out of context. Remember that sunscreens as they are currently labeled are only intended to decrease sunburn, not prevent tanning, skin cancer, aging - or bad breath.

Sunscreens could indeed do more. There are several new UVA photoprotective ingredients currently awaiting approval by the Food and Drug Administration and addition to the sunscreen monograph. These substances have been widely used in European and South American markets, but they cannot be used in the United States. Since UVA radiation is largely responsible for skin aging and the promotion of skin cancer, these new filters are needed for sunscreens to deliver on consumer expectations.

It is unrealistic for manufacturers to deliver sunscreens without the proper filters. It is my hope that new photoprotectants will be forthcoming in the United States and that these will make sunscreens better.

Many dermatologists tell patients that the best activity to preserve healthy skin is the use of sunscreen. It is important to make patients aware of sunscreen limitations. Again, sunscreens were never intended to prevent sunburn, tanning and skin cancer, and they do not prevent sunburn, tanning and skin cancer. They are the best we have at the moment, but progress is needed to develop products to meaningfully preserve skin health.

Zoe Diana Draelos, M.D., is a Dermatology Times editorial adviser and consulting professor of dermatology, Duke University School of Medicine, Durham, N.C. Questions may be submitted via e-mail to zdraelos@northstate.net
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