May 14, 2010 -- The sunlight that comes into the driver's side of cars in the U.S. may contribute to the development of skin cancers on the left side of the face and body, a new study shows.

Researchers examined the records of 1,047 patients referred to a skin cancer unit at Saint Louis University School of Medicine. The researchers say they detected more left-sided skin cancers than right-sided in both sexes, though the effect was stronger in men.

"We tend to see more skin cancer on the left side of the face," says Scott Fosko, MD, chairman of dermatology at Saint Louis University School of Medicine and co-author of the study. "The cumulative effect of being exposed to the sun builds up over many years."

The study is published in the Journal of the American Academy of Dermatology.

Fosko says people should wear sunscreens that block both UVA and UVB rays on a daily basis to avoid skin cancer. Checking the label of the product allows people to make sure the sunscreen protects against both.

A Saint Louis University news release on the study says carpooling mothers and daily commuters need to be concerned, not just professional drivers.

Sunscreens, he says, also offer protection against premature wrinkling and aging. Fosko also recommends that drivers wear protective clothing when possible, and says tinting car windows and using UV filters on the glass also could help reduce harmful UV rays.

"Professional drivers learn to wear proper safety equipment, be it gloves, steel-toed boots or safety glasses when appropriate," Fosko says in the news release. "Sunscreen should be added to the list. An ounce of sunscreen applied as prevention on the road can be worth a lot of time and expense parked in a doctor's office later on."

The researchers found that in people of both genders with skin cancers: