After a long bath, your fingertips turn wrinkly like raisins. But it is not just soggy skin. Your body does it.
What makes the wrinkles?
When your hands soak in water, your nerves tell tiny blood vessels in your fingertips to get narrower. So each fingertip shrinks a little and pulls the skin on top into wrinkles.
How do we know?
If the nerve in a finger is damaged, that finger stays smooth in water. That is why doctors can use soaking as a simple nerve test.
What are they for?
Some scientists think the wrinkles help you grip wet things, like the treads on a tire. In one test, people with wrinkly fingers picked up wet marbles faster.
Sources
- Wikipedia: Water-immersion wrinkling
- Scientific American: Why Do Our Fingers and Toes Wrinkle During a Bath?
- The Scientist: The Science Behind Pruney Fingers
- Popular Science: Why do our fingers wrinkle in water?
- Newcastle University: Get a grip: why we get wrinkly fingers and toes
- JAMA Neurology: Skin Wrinkling on Immersion of Hands: A Test of Sympathetic Function
- ResearchGate: Water-induced finger wrinkles improve handling of wet objects
