A new study sheds light on why fingers wrinkle in water—and why those wrinkles appear in the same places every time. Biomedical engineer Guy German of Binghamton University in New York wanted to know if pruney fingers always wrinkle the same way after water exposure. To find out, he and a graduate student asked three people to soak their hands in warm water for 30 minutes, photographed the resulting wrinkles, and repeated the process a day later, per Science News.
After overlaying the images for their research published in the Journal of the Mechanical Behavior of Biomedical Materials, the team found that the wrinkles lined up almost perfectly from one day to the next. Analysis revealed the folds typically followed the paths of blood vessels beneath the skin, which rarely change position. This consistency suggests that each person's wrinkly pattern is unique and stable over time, similar to fingerprints.
The admittedly small study challenges the common belief that wrinkling is caused by the skin simply absorbing water. That theory was questioned by scientists nearly a century ago who found that people with nerve damage in their fingers didn't prune up the way others did, "suggesting that it wasn't the passive movement of water causing these patterns, but an active response of the body's sympathetic nervous system," per Live Science.
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In reality, prolonged soaking leads to a drop in salt levels in the skin, prompting nerves to signal the brain, which then tells blood vessels to constrict. That constriction, in turn, tugs at the skin, creating those familiar grooves. The evolutionary reason may be that textured skin improves grip in wet conditions. German notes it's still unclear whether wrinkle patterns stay constant throughout an entire lifetime. If they do, wrinkled finger patterns might one day be used for biometric identification or forensic science. (This content was created with the help of AI. Read our AI policy.)
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