Why do we get prune fingers at the pool?

At Valley Mill Camp in Germantown, Md., a group of 9-year-old girls hovered at the edge of the pool, examining their fingertips.

Prunes.

But why? These swimmers had some of their own explanations for why their digits were shriveled like dried plums. Sophia Cordes of Washington, D.C., suggested that your fingers wrinkle up “because the water (in the pool) sort of soaks the water out of your skin.”

It sure looks like that’s what’s going on.

The reason your paws get puckered is actually fairly simple – but for the opposite reason than you may think.

“Most people are under the impression that you’re losing fluids or water – but it’s actually increased absorption,” said Cheryl Burgess, a Washington, D.C., a dermatologist.

So your fingertips may look dried out like a prune in the sun, but they actually get creased because they are absorbing a lot of water. They do this because the skin on the palms of your hands and the soles of your feet is thicker and tougher than the skin elsewhere on the body. Those skin cells also contain more protein, called keratin, than skin cells elsewhere. These tough, keratin-rich cells pull in more water than skin cells on, for example, your thigh or cheek.

We know your next question: If the skin on your finger pads is absorbing all that water, why aren’t your fingers puffing up? Because the layers of skin under the top layer are not absorbing water. So you have a layer of skin cells that’s plumped up attached to a layer of skin cells that is not – and the top layer doesn’t have anywhere to expand. So it puckers.

You water lovers out there needn’t worry, either. “It doesn’t do damage to the skin,” Burgess said. “Our skin is very protective.”

But there is something you should do when you get prune fingers. When you get out of the pool or the tub, all that water in your skin evaporates out of the cells – and that leaves your skin dry. Slather on some lotion, and you’ll be as good as new.