You might think that playing in the pool or soaking in the tub makes your fingertips and toes waterlogged and soggy. Not so! The prune effect is caused by blood vessels shrinking just below the skin – an automatic reaction triggered by your nervous system when it senses long exposure to water. Scientists think people evolved this reaction to improve their grip and traction in wet environments. After all, pruny fingers make it easier to snag slippery fish.
When hands are soaked in water, the keratin absorbs it and swells. The inside of the fingers, however, does not swell. As a result, there is relatively too much stratum corneum and it wrinkles, just like a gathered skirt. This bunching up occurs on fingers and toes because the epidermis is much thicker on the hands and feet than elsewhere on the body. (The hair and nails, which contain different types of keratin, also absorb some water. This is why the nails get softer after bathing or doing the dishes.)
Picture Credit : Google