An itch is the body’s response to an irritant, but the evolutionary function of itching remains a mystery. Dead skin cells, hair, dust or the histamines our bodies produce during an allergic reaction trigger most everyday itches. Troublesome itching can be a symptom of skin conditions, while some itches are purely psychological. Once believed to be transmitted to the brain via the same circuitry as pain, itches actually have their own dedicated messengers. Recent research suggests we feel an itch when these specialised nerve cells release a molecule called neuropeptide natriuretic polypeptide b (Nppb). Our brain’s immediate reaction is to scratch, dislodging the irritant or at least distracting us from the itch. Oddly though, scratching often increases skin irritation so it’s best avoided or done gently.
Answered by Alex Cheung