Why do your fingers wrinkle after a long bath or swim?
The skin is a beautiful and strange organ. As the body’s largest organ, it is responsible for protecting you from sunlight, chemicals, germs… And it does all this while preserving water in your body and sensation to the touch.
Guy German, Associate Professor of Biomedical Engineering, Binghamton University, State University of New York, and his team are trying to better understand the mechanisms and functions of soft biological tissues.
We know skin gets wrinkled with age or when you pinch it. However, it is still a mystery why the skin becomes wrinkled and sometimes even discolored after you shower or stay in the pool too long.
People often think that these wrinkles are formed because the skin absorbs water, causing the skin to swell and lose its elasticity.
But researchers in the 1930s found that in people with nerve damage in the fingers, the body did not form wrinkles after bathing.
To explain what’s going on, you first need to know a little about the autonomic nervous system. Functions like breathing, blinking, heartbeat or constricting pupils in sunlight all take place without you having to consciously control them thanks to the autonomic nervous system.
It also automatically controls the expansion and contraction of your blood vessels. Usually, heat, medications, or what you eat or drink can cause blood vessels to widen or narrow.
Narrowing of blood vessels is also the cause of wrinkled skin after a long swim.
When your hands and feet are exposed to water for a few minutes, the sweat ducts in the skin open, allowing water to flow into the skin tissue. This additional water reduces the percentage of salt in the skin. Nerve fibers send messages about lower salt levels to your brain, and the autonomic nervous system responds by constricting blood vessels.
The constriction of blood vessels causes the overall volume of the skin to decrease, causing the skin to wrinkle into those pronounced wrinkles. It’s like a plump grape turning into a raisin and its appearance takes on a wrinkled appearance – more volume is lost than surface area.
This constriction of blood vessels also causes the skin to become paler – the opposite of what happens when your skin becomes redder in a hot bath, because blood vessels dilate. The discoloration will be more pronounced in people with lighter skin tones.
However, in people with nerve damage, these seizures do not occur. The blood vessels never constrict, so wrinkles never appear even if you soak for a very long time.
Researchers have found that wrinkled skin has better traction underwater than skin that is not wrinkled. A better grip allows you to grip objects more firmly. This makes walking along the underwater surface easier and less likely to slip. The scientists also found that people with wrinkled fingers moved objects 12 percent faster than people with normal fingers in wet conditions.
Going forward, Guy German’s research team has conducted research to look at changes in skin structure and function due to prolonged immersion in water, not wrinkles. They are interested in what skin analysis can do to assist forensic investigators after a case or disaster. Scientists also want to learn more about foot bath syndrome, which is skin damage caused by working in wet environments for long periods of time. They tend to affect military personnel or farmers who grow crops in flooded land, such as paddy fields.
Prolonged immersion in water makes the skin more susceptible to damage, but this weakness can take several weeks to become visible.