A: Ha! This one's easy, I thought: You probably sleep with the left side of your face smushed into the pillow. But Arthur W. Perry, MD, clinical associate professor at the Robert Wood Johnson Medical School in New Brunswick, New Jersey, and author of Straight Talk About Cosmetic Surgery, had a more interesting idea. Do you often drive? If you do, the left side of your face is probably exposed more frequently to damaging UVA rays than the right. UVA rays can travel through glass, and many sunscreens protect you only from UVB rays. The majority of people in the United States have more facial wrinkles on the left side, he says. But maybe you're a carbon-footprint-conscious pedestrian. In that case, your wrinkles are likely due to asymmetry; almost all faces have a larger and smaller side, and each is subject to slightly different movements as we talk, smile, frown, and make other facial gestures, says Haideh Hirmand, MD, clinical assistant professor of plastic surgery at Weill Cornell Medical College in New York. Some people hold one eyebrow higher or squint more with one eye than the other, resulting in a different or deeper line pattern on one side of the face. Sleeping on the same side for years can also play a role, she says.
Bottom line: Your asymmetrical wrinkling is probably due to uneven sun exposure, so be sure to use a broad-spectrum sunscreen that protects you from both UVB and UVA rays.