We’re all familiar with that wrinkled, “raisin-like” appearance that our hands and feet take on after prolonged exposure to water. Maybe you’ve noticed that your fingers are wrinkled after you wash the dishes, or maybe you’ve wondered why your feet were wrinkly after a leisurely bath. So why does it happen?
We talked with Dr. J. Morgan O’Donoghue, a nationally recognized, board-certified dermatologist, to get to the bottom of this wrinkly question.
“The ‘pruney’ change that occurs in our skin after exposure to water is found only in the areas of the hands and feet,” O’Donoghue says. He notes that—depending on the individual—this change occurs after 5 to 15 minutes of continuous exposure to water. “Physiologically, this is caused by retention of water in the top two layers of the skin, the epidermis [and to] a lesser extent, the dermis.”
But when your entire body is exposed to water, why aren’t your arms, legs, or other body parts affected as well? O’Donoghue says that it isn’t entirely clear why this change is limited only to fingers, palms, toes and the soles of the feet.
“Researchers have shown that once this swelling occurs, certain small objects can be picked up more accurately and easily than [with] wet hands without these swellings. Much like a tire with treads can grip a wet road much better than a bald tire, this [swelling] may have served as an evolutionary advantage particularly for hunters and gatherers who may have benefited while foraging for wet vegetation,” he says.
O’Donoghue also notes that the central nervous system seems to play a role, as individuals with nerve damage in the hands or feet don’t get this prune-like swelling. A theory involving the narrowing of the blood vessels (known as digital vasoconstriction) is also being discussed as a possibility. Some scientists have also theorized that the wrinkling is due to water absorption in the thicker skin that is found on our hands and feet. Other areas of the body with thinner skin are thus unaffected by the absorption of water.
So the next time your skin wrinkles up in the bathtub, you won’t have to wonder about it—simply climb out of the water and wait for your smooth skin to return.