Most people are familiar with the wrinkling of fingers and toes after spending time in water—whether from a long bath or a swim, the Daily Mail reports.
A common belief is that this effect is caused by skin absorbing water and swelling. However, recent research has confirmed that the real explanation lies in the body’s nervous system and blood vessels.
Dr. Guy German, an associate professor of biomedical engineering at Binghamton University, led a study that challenges the long-held assumption that wrinkling occurs due to simple water absorption.
“Often people assume that these wrinkles form because skin absorbs water, which makes it swell up and buckle,” Dr. German noted. “To be honest, I did too for a long time.”
Instead, his research points to the autonomic nervous system—the part of the body responsible for involuntary functions like breathing and heart rate—as the key player in this phenomenon.
When hands or feet are submerged in water for several minutes, sweat ducts open and allow water to enter the skin tissue. This dilutes the salt concentration within the skin. In response, nerve fibers send signals to the brain, which triggers the autonomic nervous system to constrict the small blood vessels beneath the skin.
This constriction reduces the overall volume of the skin while its surface area remains largely unchanged. As a result, the skin puckers, forming the distinctive wrinkle patterns.
“It’s like how a dried-out grape becomes a wrinkled raisin – it’s lost more volume than surface area,” Dr. German explained.
To explore this further, Dr. German’s team had three volunteers soak their fingers for 30 minutes. They observed the wrinkled skin patterns and noted that these patterns remained largely consistent when the participants repeated the process 24 hours later. This consistency is attributed to the stable positioning of blood vessels under the skin.
Interestingly, the study also supports earlier findings that individuals with nerve damage in their fingers do not develop these wrinkles, reinforcing the role of the nervous system in the process.
Beyond the biological explanation, wrinkling may serve a functional purpose. Other studies have shown that wrinkled fingers provide better grip in wet conditions than smooth skin. This could aid activities like walking on slippery surfaces or handling wet objects, offering an evolutionary advantage in aquatic environments.
