Why Do Fingers Wrinkle in Water?

We've all seen it: take a bath or a long shower, or go swimming, and you notice the tips of your fingers and toes wrinkle. We're used to it, but do we know why this happens?

No one really understands exactly why our fingers wrinkle, though we do understand how they wrinkle.

Blood vessels and nerve endings play a role in skin wrinkling. Contrary to what many people think, the process of finger wrinkling is not osmosis. Osmosis is the flow of water from one space to another.

We know osmosis does not account for finger wrinkling for a few reasons:

• Only the skin of the fingers and toes wrinkle—osmosis would cause all skin to wrinkle if that were the explanation.
• The sympathetic nerves do not affect osmosis. If sympathetic nerves in the fingers and toes become damaged, they no longer wrinkle.
• Skin is actually impermeable to water (water can't flow in or out of skin), which is why a drop of water will evaporate when placed on the skin.

Nervous System

Sympathetic nerve activation is thought to be the stimulus that leads to the finger wrinkling. Peripheral blood vessels constrict (narrow) when the sympathetic nervous system is activated.

The sympathetic nervous system is important in the control of a number of body functions, including heart rate and blood pressure. The sympathetic nervous system is part of your autonomic nervous system, which reacts to the outside environment to keep your body stable. Exposure to water is an important trigger for the autonomic nervous system.

Blood Vessels

When small capillaries of the fingers constrict, the resulting decreased blood volume in the deep layers of soft tissue causes the skin to pull in, creating the folds that we know as wrinkles.

Immersing your hand or foot in cold or warm water causes the finger blood vessels to constrict.

Why Do Fingers Wrinkle?

There is an ongoing debate about why our bodies have developed this ability to wrinkle the skin. Wrinkling funnels water away from the skin.

The most recently proposed theory is that skin wrinkling gives you a better ability to grip objects with wet fingers. By creating "treads" similar to tire treads, wrinkled fingers can grasp wet objects better.

And researchers suggest that the rest of the body does not wrinkle when immersed in water since hands and feet are the only areas of your body that grip,

This is one recent theory, and it certainly has a lot of people thinking they've solved the mystery of wrinkled fingers and ties. But this isn't the first theory proposed to explain finger wrinkling—and it may not be the last.