Why you shouldn’t scratch itchy rashes
New research shows that scratching has two faces: it can aggravate skin inflammation, but also help the immune system fight bacterial infections.
Your parents already said it: scratching makes an itchy result even worse. And now we finally know why, thanks to new research that recently in Science has appeared.
Paradox
At first glance it seems like a paradox. If scratching is bad for you, why does it feel so nice? “Scrabbing often feels good, which indicates that it must have an evolutionary advantage,” says main author Daniel Kaplan, professor of dermatology and immunology at the University of Pittsburgh. “Our study helps to unravel this mystery.”
To scratch
Krabben is a natural, instinctive reaction to itching and plays an important role in many skin conditions and injuries, such as contact eczema and insect bites. For example, contact eczema is caused by a reaction to allergens or skin -irritating substances. This ensures an itchy, swollen rash. But no matter how tempting it is to scratch, that only makes it worse: it stirs up the inflammation, worsens the symptoms and slows the healing. Yet it probably happens to you all too often that you have ended up in a reinforcing ‘itch-crab cycle’, in which scratching intensifies the itch and further damages the skin. In contrast to pain, which usually evokes a avoidance reaction, scratching can also feel pleasant, which indicates that it might have an evolutionary advantage.
Mice
To discover what this vicious circle drives, the team caused itch -causing allergens to mice to cause eczema -like symptoms. They compared ordinary mice with mice that did not experience any itching because they miss a specific itching sensitive nerve. When normal mice had the chance to scratch, wool up their ears and filled with inflammatory cells, the so -called neutrophils. On the other hand, the inflammation was much milder with mice that could not scratch, because they wore a small collar – such a protective collar that dogs sometimes wear after a veterinarian visit – and with mice without the itching sensitive nerve. This experiment confirmed what researchers already suspected: scratching only annoys the skin.
Pain -sensitive nerves
The researchers then discovered that crabs activate pain -sensitive nerves, which release a substance called ‘Substance P’. This substance triggers manure cells that play a crucial role in inflammation and itching by attracting neutrophils. “With contact eczema, manure cells are immediately stimulated by allergens, which leads to mild inflammation and itching,” Kaplan explains. “But by scratching, substance P is released, which activates manure cells via a different road. This ensures that scratching the inflammation in the skin worsens, because manure cells are now being activated in two ways at the same time. ”
Skin microbiome
Manure cells are involved in various inflammatory disorders and allergic reactions, but they also play a crucial role in protection against bacteria and other pathogens. That is why the researchers wondered whether the activation of manure cells by scratching has an influence on skin microbiome.
Bacteria
And that is indeed the case. In experiments, the team discovered that scratching the quantity Staphylococcus aureus On the skin reduced, the most common bacterium that causes skin infections. “The fact that scratching helps against Staphylococcus aureus Suggers that scratching can have an advantage in some cases, “concludes Kaplan. “But the damage it causes to the skin will probably outweigh chronic itching than this possible advantage.”
With this study, the researchers have uncovered the double effect of scratches. Although it can worsen the skin inflammation, it can also reinforce the immune system against bacterial infections at the affected location. The researchers are now developing new treatments for contact eczema and other inflammatory -related skin conditions, such as rosacea and hives. They focus on reducing inflammation by blocking receptors on manure cells.
