Overview

• Fingertip wrinkles in water are caused by blood vessel constriction triggered by the autonomic nervous system, not by skin swelling as previously assumed.
• The wrinkles form when water enters through sweat ducts, reducing salt concentration and signaling the brain to constrict blood vessels.
• Researchers found that wrinkle patterns are highly consistent, repeating across separate water immersions 24 hours apart.
• Wrinkled skin improves grip on wet surfaces, a functional advantage that may have evolutionary significance.
• The findings, published in the Journal of the Mechanical Behavior of Biomedical Materials, have potential applications in forensic identification, biometric mapping, and diagnosing nerve damage.