Do Sunscreens Really Protect You from Melanoma?
Prevention specialists feel that sunscreen should be used only as an adjunct to habits capitalizing on natural sun protection—such as seeking shade, spending less time outdoors during the hours when the sun is most direct, and wearing protective clothing.
Sunscreens should not substitute for sensible avoidance of excessive sun exposure. They should not be used simply to increase your sun-worshiping hours.
Sunscreens do help though. A study conclusively showing their positive effects was done in Australia by Dr. Robin Marks. As reported in the Skin Cancer Foundation Journal in 1994, half the study participants wore plain cream without any sunscreen ingredients, and the other group applied lotion with a sun protection factor (SPF) of 17, effective against both UV-B and UV-A. Both groups were educated about avoiding excessive exposure to the intense Australian summer sun. The participants who applied the sunscreen had many fewer new solar keratoses, or small, flat, red, flaky growths on the skin that can be precursors to non-melanoma skin cancers. Not only that, but those participants’ existing keratoses seemed to disappear or stop growing.
Sorting Out the Sun Protection Lotions
What is the best sunscreen lotion to wear? There are two basic types: some contain chemicals to absorb ultraviolet radiation, and others rely on particles of titanium dioxide or zinc oxide to block or scatter the light. The latter products are supposedly chemical-free but in fact contain inert chemicals. Some products are a combination of the two types. For some people, the disadvantage of titanium dioxide or zinc oxide is that until you wash the stuff off, your skin is an unattractive whitish color. Now micronized versions are available that break down the ingredients into tiny particles that blend in nicely with lighter skin colors.You can take the SPF rating as an initial guide. The SPF measures the ability of a product to reduce the amount of UV-B radiation penetrating the skin. A sun protection factor of 10 reduces UV-B penetration by 90 percent, SPF 20 by 95 percent, and SPF 30 by 97 percent.
Some feel that the SPF is not accurate: because a standardized measurement system for UV-A does not yet exist, the rating does not register the ability to block UV-A radiation.You can’t put a base of SPF 7 lotion on and then an SPF 15 sunscreen on top of it and expect them to add up to a protection factor of 22. Instead, the protection factor will be the higher of the two ratings (in this case 15). Most people don’t use enough sunscreen to get effective protection or to equal the SPF rating on the bottle. Food and Drug Administration guidelines suggest one ounce of cream for each application; you can assume that a bottle of sunscreen lotion will provide eight applications. You should apply your sunscreen at least forty-five minutes before going out into the sun, to allow for better bonding to the skin. Reapply sunscreen after going into the water: rarely will the protectant maintain its efficacy after you’ve been swimming.
Source: Poole, Catherine, Guerry, DuPont, M.D., Melanoma Prevention Detection and Treatment, New Haven: Yale University Press, 2005.
UPDATED: June 6, 2014