Personal consult with Dr. Amy Wechsler, MC's resident dermatologist and psychiatrist.
Q: Is it true I need sunscreen in the shade and while driving in a car?
A: Absolutely. Shade may reduce UV exposure anywhere from 50 to 90 percent, but I've seen patients who have gotten burned from the reflection off sand, water, and pavement. Wear at least an SPF 30 daily, and if you're going to be in direct sun all day, set your cell-phone alarm to go off every three hours as a reminder to reapply — just one burn can permanently damage skin's DNA.
Driving in a car doesn't completely protect you, either. While most windshields block sunburn-causing UVB rays, they don't block UVA rays, which cause aging and melanoma. For commuters who drive at peak sun hours, I suggest getting car windows tinted with the strongest available UVA filter.