14-05-2025
Scientists reveal the real reason why your fingers wrinkle when you soak in the bath
It's a phenomenon we're all familiar with.
You go for a swim, or enjoy a relaxing soak in the bath, and soon enough your fingers and toes go wrinkly.
But have you ever wondered why this happens?
A common misconception is that our fingers wrinkle due to swelling triggered by water absorption.
Now, scientists have confirmed that this isn't the case – instead, it's all down to our blood vessels.
Guy German, an associate professor in the department of biomedical engineering at Binghampton University, New York, recruited three volunteers to soak their fingers for 30 minutes.
His team annotated the patterns of looped peaks and valleys that formed on the sodden skin.
They discovered that these patterns mostly repeated themselves when they were soaked again 24 hours later.
'Often people assume that these winkles form because skin absorbs water, which makes it swell up and buckle,' he told The Conversation.
'To be honest, I did too for a long time.'
However, it turns out it's actually our autonomic nervous system at work.
This controls our involuntary movements such as breathing, blinking and our heart beating – as well as how our blood vessels contract and relax.
Normally temperature, medication and what we eat and drink can influence how they behave.
'This contraction of your blood vessels is also what causes the skin to wrinkle after a lengthy swim,' Dr German said.
'When your hands and feet come into contact with water for more than a few minutes, the sweat ducts in your skin open, allowing water to flow into the skin tissue.
'This added water decreases the proportion of salt inside the skin.
'Nerve fibres send a message about lower salt levels to your brain, and the autonomic nervous system responds by constricting the blood vessels.
'The narrowing of the blood vessels causes the overall volume of skin to reduce, puckering the skin into these distinct wrinkle patterns.
'It's like how a dried-out grape becomes a wrinkled raisin – it's lost more volume than surface area.'
He explained that submerged fingers usually reproduce the same wrinkly pattern because blood vessels 'don't change their position much'.
The experiments, published in the Journal of the Mechanical Behavior of Biomedical Materials, also confirmed another theory – that wrinkles don't form in people who have nerve damage in their fingers.
Dr German also revealed another advantage to wrinkled fingers and toes – grip.
Researchers have found wrinkled skin can provide more grip underwater compared to unwrinkled, smooth skin.
This could make walking along an underwater surface easier, with less likelihood of slipping.
