News Health & Medicine Wet fingers always wrinkle in the same way The folds follow the paths of blood vessels Finger wrinkle patterns induced by a long soak stay consistent over time, a new study suggests. sellyhutapea/Getty Images By McKenzie Prillaman 3 hours ago Summertime soaks in the pool often leave fingertips shriveled and pruney. Each time someone goes for a dip, their digits wrinkle in the exact same patterns, researchers report in the May Journal of the Mechanical Behavior of Biomedical Materials. That’s because the folds follow the paths of blood vessels below the skin’s surface, which generally stay in place. Many people think that fingers and toes wrinkle when wet because the skin swells when it absorbs water. But around 20 years ago, researchers discovered that the puckering comes from blood vessel constriction. A prolonged soak leads to water entering the skin and diluting the amount of salt in the tissue, which gets signaled to the brain via nerves. The brain then instructs stationary blood vessels to narrow, pulling in the anchored overlying skin in fingers and toes. It’s an evolutionary mechanism that boosts grip strength under water by creating texture. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday.