Why do we itch?

The sensation of itching is caused when something irritates the skin, which can be caused for a variety of reasons.

All animals itch, and we know from personal experience how irritating and unpleasant a bout of itching can be. We can itch for a variety of reasons, including, but not limited to dry skin, skin irritation, dirty skin, insect bites, disease, parasites such as lice, or even for psychosomatic reasons. Itching can also be a common symptom associated with many diseases, such as malignancy, infection, and metabolic disorders. It is also a common symptom of allergies, psoriasis, stress, chicken pox, kidney disease, jaundice, pregnancy, anaemia and fear.

The sensation of itchiness may have evolved as an evolutionary response. According to scientists, itchiness serves an inherent purpose. It allows one to get rid of irritants, and to preserve the skin’s health. Historically, it may have helped get rid of parasites on the skin.

Itching occurs when something irritates the skin, such as bugs, dust, clothing fibers and hair. The irritation can be a mild tickling sensation. Image, when a stray hair brushes past your shoulder. The receptors in that area then pick up on the signal and transfer the signal to the spine where it is processed and forwarded to the cerebral cortex in the brain. The brain then prompts us to scratch the affected area in order to remove the irritant from the skin.

Most itches are caused by an irritant, however, some itches are psychosomatic, which means that nothing is there but we think there is and we continue to scratch nonetheless. Often this is the hairs on our body irritating the skin, but if it happens frequently, it could be due to an underlying psychological issue. Itches can also be contagious, similar to yawns, wherein if we see someone scratch an itch, we tend to feel itchy in the same place.

The itch has many similarities to pain, starting with the fact that they are both unpleasant and unwanted sensory experiences. However, their behavioral response patterns are different, as pain causes a withdrawal reflex, i.e. we instinctively move away from the thing causing us pain, while the itch causes a scratch reflex leading us to instinctively scratch the area instead. In fact, itching has its own special nerves and system in place.

While starching an itch gives immense satisfaction and relief, it can also increase the likelihood of the person accidentally breaking skin, leading to scabs and infections. In fact, the relief caused by scratching is temporary, as it only distracts the person from the itch by causing a slight pain for the nerves to focus on instead. 

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