It is one of those small body changes most people barely question: spend a few minutes in the bath, pool, or sink, and your fingertips start to look crinkled. For years, the easy explanation was that the skin simply soaked up water. But researchers have found that the real reason is more active, and more interesting, than that.
Water does affect the outer layer of skin, but the deep, familiar wrinkling on fingers and toes is not just a case of swelling. The process is closely tied to the nervous system and changes in blood flow beneath the skin.
What Really Happens Under the Skin
After your hands or feet stay in water for several minutes, small blood vessels in the fingertips begin to narrow. This is called vasoconstriction.
As those tiny vessels constrict, the volume under the skin decreases slightly. The skin surface then folds into the wrinkle pattern most people recognize after swimming, bathing, or washing dishes for a while.