Blocking Sunburn Damage? Q. After shaving my head I spent a weekend in the Rocky Mountain sun. Despite putting on SPF 30, I woke up Monday morning with a blistering, crusty, pus-spewing top. It redefined the term "boogerhead" as I flaked off the yellow scabs. Now it's better and the skin is just peeling, but do I have anything to be concerned about? The incidence of skin cancer is rising at an alarming rate, with ultraviolet (UV) radiation from the sun the major cause. One reason may be the weakening effect of atmospheric pollution on the Earth's protective ozone layer, which allows more intense solar radiation to reach us. Even though UV waves are longer and have less energy than ionizing forms of radiation like X-rays, they are still powerful enough to penetrate living cells and cause DNA damage. UV radiation doesn't just hurt the skin; it can contribute to the loss of vision as you grow older by damaging the retina (macular degeneration) and the lens (cataract). I always recommend protecting yourself in as many ways possible: Stay out of the sun when it's at a high angle in the sky; this is when the UV rays are more energetic and more numerous (from 10 a.m. to 4 p.m.). Choose clothing that covers your skin - brimmed hats, lightweight, long-sleeved shirts. Use a powerful sunscreen (SPF 15, at least) and wear UV-protective sunglasses. And finally, take antioxidants to help block the chemical reactions that can trigger cancer's uncontrolled cell growth. Living in the Arizona desert, I have to follow this advice year-round. Cancer risks increase with cumulative exposure, so you should definitely avoid getting another burn on your head. The more bad burns you get, especially in your teenage years and in your 20s, the higher your risk of skin cancer as you age. If you stop getting burned, you will lessen the danger. Most dermatologists say it's a good idea to get in the habit of putting a high-SPF sunscreen on every morning. I agree. But as you've found, sunscreen can give you a false sense of protection. Just because you're wearing sunscreen, don't assume you can spend infinite time in the sun. It's still good to be careful. An old-fashioned sunscreen that is still effective is zinc oxide. This is an opaque cream that provides a mechanical barrier to sunlight. (It's available in white or in neon colors now.) It works extremely well, but most people don't want to walk around with their faces completely white (or electric blue). If you get burned, aloe is probably the most soothing treatment. You can buy bottles of the pure gel in health-food stores, or grow the plants around your house.