Got pruney fingers? Here’s the scientific skinny to explain it

As swimming season heats up, you might notice your fingers wrinkle after spending time in the water—turns out, those wrinkles are the same with every dip you take.

And that, researchers from Binghamton University, State University of New York, could have useful applications for crime investigators.

Guy German and his team at SUNY’s Biological Soft Matter Mechanics Laboratory discovered that the wrinkles come from blood vessels contracting under the skin and not from skin swelling, as folks once thought.

German had previously studied this in 2023, he explained, but a student’s follow-up question inspired more research.

“A student asked, ‘Yeah, but do the wrinkles always form in the same way?’ And I thought: ‘I haven’t the foggiest clue!’ ” said German, who teaches biomedical engineering at the Thomas J. Watson College of Engineering and Applied Science.

In a study published in the Journal of the Mechanical Behavior of Biomedical Materials, German and graduate student Rachel Laytin probed what’s really going on in a phenomenon people sometimes describe as “getting pruney.”

They had participants soak their fingers in water for 30 minutes, photographed the wrinkles, then repeated the test at least 24 hours later. They found the same patterns of raised loops and ridges both times.

“Blood vessels don’t change their position much—they move around a bit, but in relation to other blood vessels, they’re pretty static,” German said. “That means the wrinkles should form in the same manner, and we proved that they do.”

The team also found something surprising.

“We’ve heard that wrinkles don’t form in people who have median nerve damage in their fingers,” German said. “One of my students told us, ‘I’ve got median nerve damage in my fingers.’ So we tested him—no wrinkles!”

The research could be useful in forensics to help with fingerprinting or identifying bodies after water exposure. As a former police officer, German’s dad faced some of these challenges during his career.

“Biometrics and fingerprints are built into my brain,” he said. “I always think about this sort of stuff, because it’s fascinating.”

German and his students are eager to keep exploring skin science.

“I feel like a kid in a candy store, because there’s so much science here that I don’t know,” he said.

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