Binghamton Scientists Discover the Surprising Reason Your Fingers Wrinkle in the Bath

If you’ve ever soaked in a warm bath or taken a dip in the pool, you’ve likely noticed your fingers and toes turning pruney.

For years, many of us assumed this wrinkling was caused by our skin simply absorbing too much water and swelling. But new research from Binghamton University reveals that theory doesn’t hold water.

Binghamton-Led Study Points to the Nervous System

Guy German, an associate professor in the Department of Biomedical Engineering at Binghamton University, led a study to get to the bottom of this everyday mystery. His team recruited volunteers to soak their fingers for 30 minutes and then analyzed the patterns of wrinkles that formed. When they repeated the experiment 24 hours later, they found that the wrinkle patterns largely repeated, indicating the changes weren’t random or caused by swelling alone.

“We often assume the skin just swells and buckles from absorbing water,” German explained in The Conversation. “To be honest, I did too for a long time.”

The Real Wrinkle Culprit: Blood Vessels

Turns out, the wrinkling effect is actually controlled by our autonomic nervous system—the same system that regulates involuntary functions like breathing, blinking, and heartbeat. When your hands or feet are exposed to water for several minutes, the sweat ducts open up and allow water to enter the skin tissue. This decreases the salt concentration in the skin and triggers a response: your blood vessels constrict.

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That constriction beneath the surface causes the skin above to wrinkle. It’s your body actively responding to the water, not a passive effect of absorption.

Functional Reason Behind the Prune Look

Dr. German also shared that these wrinkles may have a purpose beyond confusing bath-takers. Studies suggest wrinkled skin actually improves grip in wet conditions. Think of it like treads on a tire, pruny fingers and toes might help us better grasp wet objects or navigate slick surfaces underwater.

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So, the next time you step out of the tub and glance at your wrinkled fingers, give a little nod to your autonomic nervous system, and to the Binghamton University researchers helping us understand how amazing our bodies really are.