New study explains why you should not scratch itchy results

New research published in the diary Science Discover how crabs worse inflammation and swelling in a mouse model of a type of eczema called allergic contact dermatitis.

“In the first instance, these findings seemed to introduce a paradox: if scratching an itch is bad for us, why does it feel so good?” Senior author Daniel Kaplan, MD, Ph.D., professor of dermatology and immunology at the University of Pittsburgh.

“Scratching is often pleasant, which suggests that, in order to evolved, this behavior must offer a kind of benefit. Our study helps to resolve this paradox by providing evidence that also offers scratches against bacterial skin infections.”

Allergic contact dermatitis is an allergic reaction to allergens or skin -irritating substances – including gifsumak and certain metals such as nickel – that leads to an itchy, swollen rash. Success in the often irritable urge to scratch triggers further inflammation that worsens the symptoms and slows the healing.

To find out what drives this vicious circle, Kaplan, first author Andrew Liu, student in Pitt’s Medical Scientist Training Program, and their team used itching-inducing allergens to cause eczema-like symptoms on the ears of normal mice and not itching Because they don’t have itch neuron.

When normal mice were allowed to scratch, their ears were swollen and filled with inflammatory immune cells called neutrophiles. Unlike inflammation and swelling, there were much milder with normal mice that could not scratch because they wore small Elizabethan collars, similar to a cone that could sport a dog after a visit to the veterinar. This experiment confirmed that scratches further worse the skin.

Subsequently, the researchers showed that scratches ensure that pain -sensing neurons give a connection to the name Substance P.. In turn, substance P manure cells activates that are important coordinators of inflammation that cause itching and inflammation through recruitment of neutrophiles.

“In contact dermatitis, manure cells are directly activated by allergens, which float small inflammation and itching,” Kaplan explains.

“In response to scratches, the release of fabric P manure cells activates via a second route, so the reason that scratches trigger more inflammations in the skin is because manure cells are synergistic activated by two paths.”

Manure cells are culprits in a series of inflammatory skin conditions and allergic reactions, but they are also important for protecting bacteria and other pathogens. As such, the researchers wondered whether scratches-induced activation of manure cells could influence skin microbioma.

In experiments led by co-author Marlies Meisel, Ph.D., university teacher of immunology at PITT, the team demonstrated that scratches reduced the amount of Staphylococcus Aureus, the most common bacteria involved in skin infections on the skin.

“The finding that scratches improve the defense against Staphylococcus Aureus suggests that it can be favorable in some contexts,” said Kaplan. “But the damage that scratching the skin probably outweighs this advantage if it is chronic.”

Now the researchers are investigating new therapies for dermatitis and other inflammatory skin conditions such as rosacea and urticaria that suppress inflammation by targeting manure cells.