Slathering sunscreen on children does not seem to keep them from developing moles, but putting a T-shirt on over their bathing suits may, a new study suggests.

The finding is potentially important, researchers say, because the issue of sun exposure and moles is not one of cosmetics. Moles - or melanocytic nevi - can, in a small number of cases, eventually develop into melanoma, the deadliest form of skin cancer.

The study of more than 1,800 German children ages 2 to 7 found no clear relationship between sunscreen use and the number of melanocytic nevi the children had.

On the other hand, those who often wore T-shirts and shorts at the beach or pool did tend to have fewer moles than children who typically wore only bathing suits.

That doesn’t mean, however, that parents should abandon sunblock, said the study’s lead author, Dr. Jurgen Bauer of the University of Tubingen in Germany.

Sunscreen, he told AMN Health, protects against the ultraviolet rays that contribute to the various forms of skin cancer, so parents should continue to use them.

“However,” Bauer added, “our study and other studies show that sunscreens do not protect as strongly as expected against moles.”

He and his colleagues report their findings in the April issue of the American Journal of Epidemiology.

Moles are extremely common, particularly among light-skinned people, and the vast majority will never develop into melanoma. Genes are a strong determinant of how many moles a person will develop, regardless of sun exposure; the more moles parents have, the more their children are likely to have.

People with a large number of normal moles are also thought to have a greater-than-average risk of melanoma.

So although a child’s moles should not scare parents, Bauer said, it still “makes sense” to take measures to prevent mole development. Based on the current findings, covering children up when they’re at the beach, poolside or backyard is one way to do that.

The study included 1,812 children between the ages of 2 and 7 from German day-care centers. The researchers counted the number of moles on both the children and their parents, and asked parents whether they covered their children with sunscreen or extra clothes during outdoor activities.

Overall, three-quarters of the parents said they “almost always” put sunscreen on their children. A similar percentage said their children usually wore T-shirts over their bathing suits when at the beach or outdoor pool; about 17 percent said they also had their children wear shorts.

In general, Bauer and his colleagues found, the more clothing the children wore under the sun, the fewer moles they had. There was no such effect seen with sunscreen use.

However, the researchers point out, the protection provided by sunscreen depends on whether it’s properly used. Bauer said that another phase of his team’s research is to see whether giving parents free sunscreen and education on its use makes a difference in their children’s mole count. The results of that work will be available soon, he said.

Based on the present findings, the researchers say, seeking shade and adding clothes are the best ways to protect children’s skin. Using sunscreen is still important - especially on exposed areas like the face and hands - but, Bauer’s team writes, “Parents should be advised to not rely solely on sunscreen for sun protection.”

SOURCE: American Journal of Epidemiology, April 1, 2005.