Why Do You Get Wrinkly When in Water for a Long Time?

Too much time in the water can leave you looking like a prune. Different theories attempt to explain why water exposure leads to wrinkly skin, including suggestions that the wrinkles are caused by water absorption or even by blood vessels. But according to a June 2011 article in "Nature News," a different hypothesis is offered. The answer, per Mark Changizi, who works as an evolutionary neurobiologist in Boise, Idaho, has to do with evolution.

Water Absorption

• The water absorption theory explains that the three layers of skin play a role in the wrinkly-prune look you get after a bath or a swim in the pool. How this works is that the dead keratin cells on the outer layer of the skin -- the stratum corneum -- absorb the water. The absorption makes the skin's surface area swell. Since the stratum corneum is tightly connected to the living tissue, a wrinkle effect occurs, because the living tissue must compensate for the expanded surface area.

Evolution

• The most recent theory on the wrinkly fingers from water effect relates to evolution and adaptation. Mark Changizi and his scientific team believe that the wrinkles occur as a means of creating a no-slip grip for the fingertips. According to the theory, when conditions are slippery the adaptive response is to help the fingers and toes grip onto surfaces without slipping away. This, perhaps, comes from an innate survival tactic of the body. Changizi compares the wrinkles on the skin to rain treads on tires.

Blood Vessels

• Another theory about wrinkly fingers and toes from the water is offered by Xi Chen, a biomechanical engineer at Columbia University. Chen explains that the cause for the prunelike skin has to do with blood vessels. When skin is immersed in hot water, blood vessels constrict, causing the tissue to shrink in relation to the outer skin. The result is a contraction between the tissue and the skin that causes the skin to buckle.

Feet and Hands

• Just as there are different theories for the wrinkling of hands and feet from water, there are varying explanations for why just the hands and feet -- namely the toes and fingertips -- get wrinkled. Other parts of the body do not seem to be affected by the wrinkles. One idea on this phenomenon is that it's due to the thicker skin on other parts of the body. The evolutionary theory explains that since fingers and toes are used for gripping, other parts of the body do not need the anti-slip grip assistance.