Research shows that fingers wrinkle in a consistent pattern each time they are immersed in water.
Do your wrinkles always form in the same pattern after spending too much time in water? New research from Binghamton University, State University of New York, says they do.
A few years ago, Binghamton University Associate Professor Guy German investigated why human skin wrinkles during extended water exposure. The common belief was that water caused the skin to swell, leading to wrinkling, but there was little scientific evidence to support that idea.
German and his team at the Biological Soft Matter Mechanics Laboratory discovered that after your skin has been in water for a while, the blood vessels underneath actually shrink. This contraction pulls the skin inward and creates the familiar wrinkled effect.
A student's question sparks new inquiry
He wrote about the research for The Conversation -- a nonprofit news organization that asks academics to share their expertise on current topics -- as part of its Curious Kids feature. One of the follow-up questions stumped him, though.
"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, a faculty member at the Thomas J. Watson College of Engineering and Applied Science's Department of Biomedical Engineering. "So it led to this research to find out."
In a paper recently published in the Journal of the Mechanical Behavior of Biomedical Materials, German and Rachel Laytin '23, MS '24, show that, yes, the topography patterns remain constant after multiple immersions.
"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."
Method: water tests and image comparison
The research put subjects' fingers in water for 30 minutes, taking photos and then repeating the immersion under the same conditions at least 24 hours later. By comparing the images, German and Laytin found the same patterns of raised loops and ridges after both immersions.
They also made an interesting side discovery: "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!"
As much fun as it was to figure out something a child asked, the research also could have real-world applications in forensics, such as fingerprinting at crime scenes and identifying bodies found after prolonged water exposure. German's father, a retired U.K. police officer, faced some of these challenges during his law enforcement career.
"Biometrics and fingerprints are built into my brain," he said. "I always think about this sort of stuff, because it's fascinating."
German is eager to further explore questions about skin immersion with his students: "I feel like a kid in a candy store, because there's so much science here that I don't know. We thank the people at The Conversation and the wonderful question they asked us, because does it create cool new science."
Reference: "On the repeatability of wrinkling topography patterns in the fingers of water immersed human skin" by Rachel Laytin and Guy K. German, 13 February 2025, Journal of the Mechanical Behavior of Biomedical Materials.
DOI: 10.1016/j.jmbbm.2025.106935