While scratching an itch might offer immediate relief, it can paradoxically worsen the sensation and prolong discomfort, according to new research. Doctors have long advised against scratching, noting that it can damage the skin, but scientists are now gaining a clearer understanding of the cellular mechanisms behind this common urge and its consequences.
Researchers studied the effects of scratching on mice with induced skin irritations, such as allergic contact dermatitis. In experiments, mice were fitted with devices that prevented them from scratching itchy spots on their ears. The findings indicated that mice unable to scratch experienced significantly less swelling and fewer inflammatory cells at the site of irritation compared to those that could scratch.
Daniel Kaplan, a dermatologist at the University of Pittsburgh whose lab conducted the research, explained that these findings align with everyday human experience. He noted that a mosquito bite, if left unscratched, typically resolves within minutes for most people. However, he added, "But if you start scratching it, it’s your friend for a week," becoming itchier and more inflamed.
The study also shed light on why scratching provides a fleeting sense of relief. The researchers suggest that this relief, though temporary, might be linked to an evolutionary response possibly related to germ protection. However, this immediate benefit does not outweigh the long-term negative effects of scratching.
The instinct to scratch is not exclusive to humans or other mammals; even fish exhibit this behavior, suggesting an ancient evolutionary basis. Despite the immediate gratification, the cellular-level response initiated by scratching ultimately contributes to a more persistent and intensified itch, creating a cycle that can be difficult to break.