In the event of itching, scratching reduces the presence of potentially dangerous bacteria on the skin.
- A itching, the sensation that stimulates scratching behavior, is often triggered by skin irritants and inflammation.
- The removal of itching detection neurons or the physical prevention of scratch decreases the inflammation associated with the responses of mastocytes, white blood cells that play a central role in the triggering of allergy symptoms.
- Gutting encourages sensitive pain in pain to release a neuropeptide, the substance P, which stimulates mast cells.
Mosquito bite, glass wool, humidity, yeast infection, hormonal changes … Several factors can cause itching and make you want to scratch. When we are small, our parents keep repeating to us that you should not rub your skin with your nails, because it worsens the situation. However, according to a new study, published in the journal Sciencescratching where it itches is not such a bad idea as that. In order to achieve this conclusion, scientists from Washington University in Saint-Louis (United States) wanted, at first, to understand why we scratch ourselves.
Scratching more inflammation, because “mastocytes have been activated”
To carry out the work, the researchers put a synthetic allergen on the mouse ears. This induced a form of skin inflammation called “allergic contact dermatitis”, which is caused by contact with an allergen like the oil contained in the poisonous sumac. When rodents scraped, their ears swelled and filled with neutrophils, a type of immune cell. On the other hand, the ears of animals cannot do so due to tiny Elisabethans necklaces, similar to those that dogs wear after a visit to the veterinarian, were less swollen and contained less neutrophil. Mouses from bio-engineering devoid of a neuron itching detector had an equally discreet reaction. Thus, scratching aggravates inflammation.
In order to go further, the team examined normal rodents allowed to scratch their ears. She noticed that in scraped places, pain sensitive to pain released a powerful messenger of the nervous system, the substance P. In turn, the substance of key white blood cells, called mastocytes, which play a central role in the trigger of allergy symptoms. Mastocytes have recruited neutrophils in the scraped area, which caused inflammation. “In contact dermatitis, mastocytes are directly activated by allergens, which causes inflammation and minor itching. In response to scratching, the release of substance p activates mastocytes by a second way, therefore the reason for which the scratch triggers more inflammation in the skin is that mast cells have been activated in a synergistic way by two ways “, explained Daniel Kaplanauthor of research.
Scratching reduces the quantity of Staphylococcus aureus on the skin
Although mastocytes are the source of various inflammatory skin diseases and allergic reactions, they can also protect us from bacteria and other pathogens. And for good reason, scientists revealed that scratching reduced the quantity of Staphylococcus aureusthe most common bacteria involved in skin infections, on the skin. “Gutting could be beneficial in certain contexts. But the damage caused by scratching is probably prevailing on this advantage when itching is chronic.”
From now on, the team is studying new therapies against dermatitis and other inflammatory skin diseases, such as rosacea and hives that suppress inflammation by targeting mastocytes receptors.
