Sunscreen Prevents Precancerous Spots
Daily Sunscreen Use Fights Early Signs of Skin Cancer
April 21, 2003 - Applying sunscreen every day rather than only on sunny ones makes a big difference when it comes to fighting the first signs of skin cancer. A new study shows that daily use of sunscreen is much more effective than sporadic use in preventing precancerous skin growths called solar keratoses or SKs.
The skin lesions are the earliest forms of the most common types of skin cancer caused by sun exposure, basal cell carcinoma and squamous cell carcinoma. People who have SKs are up to 12 times more likely to develop these forms of skin cancer than others.
Despite these risks, researchers say little is known about sunscreen's role in preventing these early markers of skin cancer. In this study, researchers compared the effects of daily versus occasional use of sunscreen use in reducing the number of SKs in 1,621 adults living in Queensland, Australia from 1992 to 1996.
One group was instructed to apply a water-resistant sunscreen with an SPF (sun protection factor) of 16 each morning to their head, neck, arms, and hands, and the other group was told to use sunscreen at their own discretion.
People who used sunscreen daily developed significantly fewer SKs than the occasional sunscreen users, and the protective effects of daily sunscreen use were especially strong in the first two and a half years of the study.
For example, the increase in SK counts from 1992 to 1994 in the group that used sunscreen daily was about 24% lower than the increases found in the occasional-use group. Researchers say that reduction is equivalent to preventing one precancerous growth per person over the four-year study.
The findings appear in the April issue of the Archives of Dermatology.
But researcher Steven Darlington and colleagues from the Queensland Institute of Medical Research in Australia say their study may actually have underestimated the protective effects of sunscreen in preventing skin cancer because it didn't compare daily sunscreen use to not using sunscreen at all. Due to the well-known risks of skin cancer in a subtropical environment such as Australia, researchers opted to allow their comparison group to use sunscreen as they would normally.
Dermatologist Arielle Kauvar, MD, says these findings are encouraging because the protective effects of sunscreen in reducing skin cancer risk were especially dramatic in people that were younger or tanned easily.
"That tells us if you start using sunscreen on a regular basis when you're young or before you have any visible skin damage that it will have a better effect," Kauvar tells WebMD. "But it also had an effect on people with preexisting damage."