Why do itches feel good

At first glance, itch and pain seem to be related. The skin is studded with an array of nerve endings called nociceptors whose job is to relay information about the presence of potentially damaging stimuli to the spinal cord and brain. A weak assault on those neurons results in an itch, while a fully fledged attack results in pain. Then there is the more chronic, pathological type of itch that could be associated with dry skin, eczema, psoriasis, or other skin diseases.

Brain tumours, multiple sclerosis, chronic liver disease, lymphoma, Aids, and hyperthyroidism have all been associated with chronic itch, as have diseased neurons. Then there are the psychological and cognitive factors, but not all are as creepy as delusory parasitosis.

An obsessive need to scratch can be a manifestation of obsessive-compulsive disorder; in these cases, persistent scratching can damage the skin and only serves to exacerbate the problem. The pain from a scratch is very different from one we might feel when we put a finger in a naked flame Credit: iStock. That the itch sensation can be reduced by the application of painful stimuli only makes it an even more curious phenomenon. Scratching is a relatively minor form of pain, but the light pain we experience raking our nails across our skin does seem to help, as does the application of cold, or heat, capsaicin the chemical that gives peppers their heat , or even a few electrical zaps.

This means, paradoxically, that analgesics, which are meant to reduce pain, can actually enhance itch. When something hurts, our body responds with its withdrawal reflex. But the scratching reflex brings attention towards, rather than away, from the affected skin.

That actually makes good sense, and points to one possible evolutionary origin for the scratching reflex: closer inspection and a quick scratch is more effective at removing a crawling insect than would the withdrawal reflex. Scratching is a good way to remove not just insects and parasites, but also bits of plants and any other unwanted material hitching a ride on your skin or in your hair.

That release provokes the nociceptors in the skin to send a message to the spine, which then relays the message through a bundle of nerves called the spinothalamic tract up to the brain. In , researchers used a histamine injection to make the legs of their non-human primates itch while an electrode monitored what happened inside their spinothalamic tracts.

As soon as the histamine was injected, those neurons began to fire, and fast. On account of the pain triggered by the scratching, the brain releases serotonin, a hormone known to stabilize our mood, and induce feelings of well-being and happiness. However, alongside the relief it induces, research indicates that serotonin also reacts with receptors on neurons that carry itch-signals to the brain, causing those initial itch-signals to be re-triggered — leading to a vicious cycle of itching and scratching.

And, that is a problem because while scratching once might only cause minor damage to the skin , scratching repeatedly can severely damage the skin, causing it to break — leading to injuries and infections. Experts have also noticed that, much like yawning , scratching can be socially contagious too. And yet again, the explanation lies in evolution: the skin is not only exposed, but also our first line of defence.

So, when our ancestors in the paleolithic age noticed their companions scratching themselves, it would have made sense for them to do the same, in order to rid themselves of whatever insects or parasites appeared to be bothering their fellow human beings. Researchers are beginning to focus more on this area of inquiry. She is a lawyer by education, a poet by accident, and a painter by shaukh. You can find her on Instagram devruparakshit. Follow us. Newsletter Exclusive news delivered to your inbox.

Scratching My Head. Oct 2, Share. Image Credit: iStock. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. These include: Chemicals for immune response histamines and pain relief opiods Neuropeptides, which include pain-regulating messengers released within the brain, such as endorphins The neurotransmitters acetylcholine and serotonin Prostaglandins, which are lipids that, among other functions, create the sensation of pain in spinal nerve cells Stimulation by any of these agents is typically related to inflammation, dryness or other damage to the skin, mucous membranes or conjunctiva of the eye.

Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber?