The skin on our fingertips and toes shrivels like prunes when soaked for a few minutes in water. But is this an adaptation that occurred to help us in our evolutionary past? And what can it reveal about your health today?

Spend more than a few minutes soaking in a bath or paddling around a swimming pool and your fingers will undergo a dramatic transformation. Where there were once delicate whorls of lightly ridged epidermis, engorged folds of ugly pruned skin will now be found.

And according to a recently published study, this striking change is worth a closer inspection – each time your fingertips pucker in this way, the wrinkles create the same pattern.

It is the latest discovery about a phenomenon that has occupied the thoughts and work of scientists for decades. Bafflingly, only the skin on our fingers and toes wrinkles when immersed in water. Other body parts such as our forearms, torso, legs and face remain no more crinkled than they were before being submerged.

Most researchers in the field have puzzled over what causes this puckering in the first place, but more recently the question of why and what purpose it may serve, has attracted their attention.

Perhaps more intriguing still, however, is what our shrivelled fingers can reveal about our own health. Scientists have discovered changes in how our fingers wrinkle can point to diseases including type 2 diabetes, cystic fibrosis, nerve injuries and even cardiovascular problems.

It takes around 3.5 minutes in warm water – 40C (104F) is considered the optimal temperature – for your fingertips to begin wrinkling, while in cooler temperatures of about 20C (68F) it can take up to 10 minutes. Most studies have found it takes around 30 minutes of soaking time to reach maximum wrinklage, however. (Interestingly, recent research has shown that soaking your hands in warm vinegar can make your skin wrinkle far faster – in around just four minutes.)

Fingertip wrinkling was commonly thought to be a passive response where the upper layers of the skin swelled as water flooded into the cells via a process known as osmosis – where water molecules move across a membrane to equalise the concentration of the solutions on either side. But as long ago as 1935, scientists have suspected there is more to the process than this.

Doctors studying patients with injuries that had severed the median nerve – one of the main nerves that run down the arm to the hand – found that their fingers did not wrinkle. Among its many roles, the median nerve helps to control so-called sympathetic activities such as sweating and the constriction of blood vessels. Their discovery suggested that the water-induced wrinkling of fingertips was in fact controlled by the nervous system.

Later studies by doctors in the 1970s provided further evidence of this, and they proposed using the immersion of the hands in water as a simple bedside test to assess nerve damage that might affect the regulation of unconscious processes such as blood flow.

Then in 2003, neurologists Einar Wilder-Smith and Adeline Chow, who were working at the National University Hospital in Singapore at the time, took measurements of blood circulation in the hands of volunteers........

© BBC