Why do we sometimes scratch for no apparent reason?

On average, a person scratches a part of the body about twelve times a day. While some itching has known origins, others seem to come out of nowhere. So why do we scratch?

A video from the Ted-Ed YouTube channel discusses why we scratch an average of twelve times a day. First of all, this video (to be viewed at the end of the article) and relayed by the Digg site, classifies itching into four main categories which are itching caused by allergic reactions, those caused by dryness, those caused by different diseases and finally, those that still remain a mystery  » that arise for no reason or just because we are talking about itching “, can we hear in the video (in English).

One of the most classic origins of our itching is insect bites.  » When a mosquito bites you, it releases a chemical compound in your body called “anticoagulant”. This compound to which we are mildly allergic triggers the release of histamine, a chemical compound that causes our capillaries (small blood vessels) to swell, allowing faster blood flow and speeding up the immune response to this apparent threat, which explains the swelling. Histamine also triggers itching, which is why these bites cause you to scratch. “, explains the video.

If the causes of itching are relatively understood, it is the sensation of itching and especially the satisfaction that we get from scratching that remains less understood. Studies conducted in mice explain that it is the trauma, the pain that we cause by scratching that takes the place of the sensation itself by causing this satisfaction,  » almost like a distraction that creates this feeling of relief « .

The explanation in this video Ted-Ed continues with the history of our species, explaining that in terms of evolution, the main theory that explains itching is that our skin  » evolved to be very sensitive to touch, to be able to handle the risks of the outside world. Think about it, the response that causes us to scratch would repel any dangerous thing on our skin. « .

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