You probably know it’s important to protect yourself from the sun’s harmful rays at the pool or beach. But did you know you’re at increased risk from ultraviolet (UV) radiation in your car?


About 53 percent of skin cancers in the US occur on the left side of the body. Experts think this may be because drivers are exposed to UV light through the side car window. Dr. Ted Lain, board-certified dermatologist at Sanova Dermatology in Austin, cautions, “UV exposure through car windows is especially a concern in Texas, where the sun is strong all year long.”


UV rays can penetrate the skin, accelerate skin aging and cause skin cancer. Ultraviolet A (UVA) rays can damage the skin’s DNA because they reach deeper into the skin than ultraviolet B (UVB) rays. UVB rays don’t penetrate as deeply but can cause sunburn and some types of skin cancer. Car windshields block both UVA and UVB rays, but side windows have much less protection.


A recent study analyzed the UVA radiation that came through the windshield and driver’s side window in 29 automobiles. Researchers found that windshields block about 96 percent of UVA rays (on average); side windows only block about 71 percent. In other words, exposure to UVA radiation through side windows is 25 percent more than through the windshield. These findings may help explain increased rates of skin cancer on the left side of the face as well as increased rates of cataracts in the left eye.


The Skin Cancer Foundation cautions parents of babies and young children to be vigilant about sun protection in the car, pointing out that children sit in the back with exposure from side windows. A darker tint on side windows doesn’t necessarily block UVA radiation. The Skin Cancer Foundation recommends UVA-filtering window film as one solution. It can screen out more than 99 percent of UVA and UVB rays.


Dr. Lain urges parents to protect themselves and their children, both when traveling in a car and when outdoors. “Apply sunscreen to face, neck, arms and hands every morning, every day of the year — especially in the summer. Then, reapply half an hour before driving,” advises Dr. Lain.


Dr. Lain offers the following recommendations:


  • Select a sunscreen with an SPF of 30 or higher. SPF indicates the level of protection from UVB rays only. Look for “broad spectrum protection” on the label to make sure the product offers both UVA and UVB protection. Ingredients that protect from UVA rays include zinc oxide, titanium dioxide, stabilized avobenzone and ecamsule (Mexoryl).


  • Apply a thick layer of sunscreen at least 20 to 30 minutes before going outside or riding in a car. One ounce of sunscreen (enough to fill up a shot glass) is the amount recommended by the American Academy of Dermatology to cover exposed areas of the body. Use about one teaspoon on the face. Some experts advise putting on two coats of sunscreen — apply one coat, let it dry and then apply another. (Don’t use sunscreen on children younger than 6 months old; use hats and protective clothing.)


  • Reapply sunscreen at least every 2 hours or sooner if specified on the packaging. If you’re wet from sweating or swimming, reapply after 80 minutes.


  • Wear sunglasses that block both UVA and UVB rays. Be sure to check the label. The darkness of the lenses has nothing to do with the amount of UV protection. Look for a label that says “meets ANSI UV requirements” or “100% UV protection.” Sunglasses labeled “cosmetic” only block about 70 percent of UV rays. Wrap-around glasses or those with large frames help protect the eyes from the sun at different angles.


  • Protect exposed skin by wearing clothing with a tight weave (you shouldn’t be able to see your hand through the cloth) or sun protective clothing rated with an ultraviolet protection factor (UPF), which indicates the fraction of UV radiation that can penetrate the fabric. For example, a cover-up with a UPF of 50 means that only 1/50 of the UV rays get through. Sun protective driving gloves are an alternative for protecting hands that are more exposed to sun damage from holding the steering wheel.


Visit for a list of recommended products, including window protection, sunscreen, sunglasses and sun protective clothing.


-Dr. Lain recommends carrying sunscreen with you or in the car so you always have it available. “It may not be possible to apply sunscreen 30 minutes before each car trip, so applying it after you get in the car is better than nothing,” says Dr. Lain.

Be aware that sunscreen may be less effective if exposed to heat for prolonged long periods of time.


Brenda Schoolfield is a freelance medical writer who splits her time between Austin and Seattle.



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