Why fingers wrinkle after a long soak in water

For a long time, people thought wrinkles formed because the outer skin absorbed water and swelled. But in 1935, British doctors who examined patients with damaged finger nerves found that those fingers barely wrinkled, even after soaking.

Today the explanation goes like this. After fingertips have been underwater for a few minutes, the autonomic nerves send a signal that narrows the blood vessels under the skin, and as the tissue beneath shrinks slightly, the skin on top folds into ridges. Hospitals sometimes use this to check whether a finger's nerves are working.

So why would the body bother making wrinkles? In 2011 a hypothesis suggested they drain water like tire treads, and in a 2013 British experiment, people with wrinkled fingers finished moving wet marbles faster.

In 2014, however, a German research team found that wrinkles made little difference in handling wet objects. So the idea that they help us grip is a plausible hypothesis, not a settled answer.

There's also a reason wrinkles show up mainly on fingertips and toes, palms and soles. The skin there is thick and hairless, and it's packed with nerves that control how wide the blood vessels are.

Your arm or belly doesn't get pruney no matter how long it stays in water. That has strengthened the view that these wrinkles aren't just accidental swelling, but a body response limited to the parts we grip and stand on.

Once you get out of the water and dry your hands, the wrinkles fade slowly over time. It's a temporary response, so there's nothing to worry about. They tend to form faster in warm water, and the speed and depth vary from person to person.

Still, soaking your hands for a long time in detergent or hot water can strip the skin's oils and leave it rough. Wear rubber gloves for the dishes, then pat your hands dry and apply moisturizer afterward.