When you are swimming or sitting in the bathtub for an extended period of time you may notice your hands and feet start to wrinkle. Some people say their hands are “turning into raisins” when this happens.
This change in the texture of your hands is an evolutionary response that humans have that serves to improve your grip. The ridges that are created in your skin can improve your body’s ability to hold or grip things while submerged in water.
Most people will notice their skin begins to wrinkle after about 5 minutes of continuous exposure to water. If your skin does not wrinkle this could be a sign that your nervous system is not working as it should.
Why does this process take place?
Your skin is covered with a thin and clear oil called sebum that helps protect your skin. This is what differentiates your skin from a towel. When water is run on a towel, it absorbs and holds the water until it dries out, or is squeezed out. Your skin, however, does not hold water in this way and water instead runs off your hands and is not absorbed.
This may be effective for washing your hands, but with prolonged time in the water, the serum actually washes away, resulting in your skin becoming waterlogged.
Does it really improve grip?
A 2011 study by 2AI Labs examined how water was influenced by the wrinkles in your fingers. It was discovered that the wrinkles worked almost like a drainage system, allowing water to run out while raised portions of the fingers could remain dryer. The different elevations in the skin also improve your functional grip, similar to the way a car tire would.
A more recent German study however directly contradicts this. This study found that a human’s ability to handle objects does not change regardless if your fingers are wrinkled or wet, or if the object itself is wet. Regardless of these circumstances, you are always able to handle objects with your fingers the same way.
Still, if true, this is better results than you may have anticipated. Even when your fingers are wet they are still capable of gripping just the same as when they are not.