Why do we itch?

We feel the urge to scratch an itch dozens of times a day on average. There are all sorts of causes, from dry skin to allergic reactions. But some, mysteriously, have no trigger whatsoever. An itch can appear just by thinking about it!

One of the most well-known types of itching is caused by insect bites. A mosquito, for example, injects you with its saliva which stops your blood from clotting. This ‘anticoagulant’ causes an allergic reaction, releasing histamine.

Histamine swells our capillaries and increases our blood flow, aiding the immune system in dealing with dangers. It’s also what triggers the nerves that cause an itch (technically known as ‘pruritus’).

The exact mechanics of itching have yet to be understood. Studies have shown that, in mice, nerves associated with pain are what transmit the itch ‘signal’.

This subclass of nerve generates natriuretic polypetide B, which sends a message up the spinal cord to the brain and sounds the itch alarm.

Scratching an itch on our skin creates a minor pain signal that overrides the itch, effectively acting as a decoy, which allows us to feel momentary relief.

Certain chemicals activated in response, like serotonin, make it easier for the itch 'signal' to be fired up again. That's the reason scratching can actually make you more itchy, kickstarting a frustrating vicious cycle.

It’s believed that we’ve evolved to be sensitive to anything that touches our skin so that we’re attuned to immediate dangers around us. Our automatic impulse to scratch or bat away a foreign presence on our skin could potentially save us from poisonous stings.

But in an everyday setting, this sensation is little more than a nuisance we’ll have to live with. Try to see how long you can go without itching your face. It’s vexing!

For more chronic itching (the kind associated with skin conditions, emotional issues, etc.), no cure exists as not enough is known about what's going on at a neurological level. But if that impulse to scratch yourself can't be stopped, do yourself a favor and see a doctor.