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29 August 2006
Sunscreens Can Do More Harm Than Good 
When skin is exposed to sunlight, ultraviolet radiation (UV) is absorbed by skin molecules that can then generate harmful compounds - called reactive oxygen species (ROS) - that can cause skin damage and increase the visible signs of aging. To avoid the detrimental effects of the sun, sunscreens are used to block UV rays. But new research from the University of California - Riverside (UCR) suggests that unless people apply sunscreen often, the sunscreen itself can become harmful to the skin. When sunscreen is applied on the skin, the UV filter molecules contained in the sunscreen cut down the amount of UV radiation that can penetrate the skin. But over time, these filters penetrate into the skin and this is when the problems can potentially start. UCR's Kerry M. Hanson said that three UV filters (octylmethoxycinnamate, benzophenone-3 and octocrylene) which are approved by the FDA and widely used in sunscreens generate potentially damaging ROS themselves when exposed to ultraviolet radiation. Hanson emphasized that the additional ROS are generated only when the UV filters have penetrated into the skin and, at the same time, sunscreen has not been reapplied to prevent ultraviolet radiation from reaching these filters. "Sunscreens do an excellent job protecting against sunburn when used correctly," said Hanson. "This means using a sunscreen with a high sun protection factor and applying it uniformly on the skin. Our data show, however, that if coverage at the skin surface is low, the UV filters in sunscreens that have penetrated into the epidermis can potentially do more harm than good." According to Hanson, the best advice is to continue using sunscreens and re-apply them often, especially after sweating or swimming, which can wash them away. Source: University of California - Riverside
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