Wonder why fingers wrinkle under water? We finally have the answer to it
Ever noticed how fingertips and toes shrivel when they’re soaked for more than a few minutes in water? Do you wonder why that happens? Is it part of humans’ evolutionary past and can it reveal about our health?
It’s interesting to note that when we are under water, none of the body parts shrivel like that. Not the hands, legs or even face but just fingers and toes. Scientists have found out that it takes around 3.5 minutes in warm water - 40C for your fingertips to start wrinkling. In cooler temperatures like 20C, it can take up to 10 minutes for the wrinkling to begin.
Earlier, fingertip wrinkling was thought to be a passive response where the upper layers of the skin swelled as water entered the cells via a process called osmosis. In patients with injuries that had severed the median nerve, doctors studied that their fingers did not wrinkle. It’s the main nerves that run down the arm to the hand. The median nerve helps to control so-called sympathetic activities such as sweating and the constriction of blood vessels. It was thus found that the water-inducing wrinkling of fingertips was in fact controlled by the nervous system.
Doctors in the 1970s presented more evidence for this as they proposed using the immersion of the hands in water as a test of nerve damage. Later in 2003, neurologists at the National University Hospital in Singapore found that when the skin on fingertips began to wrinkle, there was a drop in blood flow in the fingers.
When our hands are immersed in water, the sweat ducts in our fingers open up to allow water in, which leads to an imbalance in the salts in our skin. This change in the salt balance triggers the firing of nerve fibres in the fingers, leading to the blood vessels around the sweat ducts to constrict. This leads to loss of volume in the fingertip, which pulls the overlying skin downwards and what we see in wrinkles then. Interestingly, the pattern of the wrinkles depends on the way the outermost layer of skin is anchored to the layers beneath it.