we know why it itches

We begin to know a little more about the cause of our itching. New research by biologists from San Diego in the United States has identified two types of itching, chemical and mechanical.

With Mathilde Fontez, editor-in-chief of the scientific magazine Epsiloonwe are talking today about itching.

franceinfo: Researchers have just understood why it itches with the mechanism behind the itching…

Mathilde Fontez: Yes, they traced all the way nervous itching. From the skin, to the neurons, which control this defense mechanism. Because it is one, it must be remembered: this unpleasant sensation has been selected to alert us to a danger. It’s a warning signal, a little lower than the sensation of pain in a way.

And what these researchers from the Institute for Biological Studies in San Diego, USA found is that there are actually two types of itching, driven by two mechanisms: one for itching chemicals – when a product irritates our skin, for example. And the other for mechanical itching – a fly tickling our arm, for example.

Two mechanisms that cause the same sensation?

The sensation is the same, the path is the same, from the skin to the spinal cord and finally to the brain. But these are two parallel circuits, which lead to two different populations of neurons.

The researchers demonstrated this effect in mice, specifically mice that were genetically engineered, to be more sensitive to touch — and therefore, more scratching in a way. They observed that by inhibiting one or the other of these two populations of neurons, the mice did indeed stop scratching. And by analyzing the brains of these mice, they were able to see the activation of these two types of neurons, depending on the type of stimulation – mechanical or chemical.

A lead perhaps, to cure diseases like eczema?

Yes, eczema or psoriasis. All chronic itching. This is the aim of these researchers, in the long term: to find substances which would make it possible to deactivate these mechanisms, in the case of cutaneous affections.

And the researchers show that it will be necessary to act simultaneously on the two circuits, on the two populations of neurons, because in the pathological case, these two circuits mix. The distinction between the two paths becomes blurred, and everything activates. This is probably the reason for the intensity of the itching: it scratches much harder. And it is also key data for the effectiveness of treatments.


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