Why Scratching a Skin Irritation Can Make It Worse

Scratching irritated skin is a natural response to an annoying itch, but new research suggests that while it may provide temporary relief, scratching can actually worsen the condition. A recent study published in Science examined how this action affects inflammation and swelling, providing new insights into the mechanisms linking itching and skin inflammation. The study's findings contribute to a deeper understanding of how scratching can amplify the problem.

The Study and Findings

Dr. Daniel Kaplan, professor of dermatology and immunology at the University of Pittsburgh, explained that although itching and the temporary relief from scratching may seem contradictory, the sensation of itch plays a protective role in human evolution by helping to defend the skin against bacterial infections.

In his study, the research team used allergens to replicate symptoms similar to allergic contact dermatitis in mice, observing how scratching worsened inflammation. In mice that were able to scratch, their ears became swollen and filled with neutrophils, immune cells associated with inflammation. Conversely, when mice were prevented from scratching—either through the use of Elizabethan collars or in mice lacking the itch-sensitive neuron—inflammation was significantly reduced. This experiment clearly demonstrated how scratching can intensify skin conditions.

The Mechanisms Behind Itching

The researchers further investigated the mechanisms underlying this process. When scratching occurs, pain neurons release a substance called substance P, which plays a key role in intensifying inflammation. Substance P activates mast cells, which are crucial for coordinating inflammation, further stimulating the recruitment of neutrophils to the affected area. These mast cells, already activated by allergens, are stimulated from two different sources, leading to increased inflammation and worsening skin conditions.

Scratching and the Skin Microbiome

Another important aspect examined in the study was the impact of scratching on the skin microbiome. Experiments revealed that scratching can reduce the presence of Staphylococcus aureus, one of the most common bacteria responsible for skin infections. This suggests that, in some cases, scratching may have a protective effect against bacterial infections. However, researchers caution that the skin damage caused by scratching—especially in cases of chronic itching—may outweigh the benefits, worsening the overall condition.

Currently, the research team is exploring new therapies to treat inflammatory skin conditions such as dermatitis, rosacea, and hives. Their goal is to suppress inflammation by inhibiting receptors on mast cells, aiming to treat these conditions without exacerbating symptoms.

Read the press release: Why You Shouldn’t Scratch an Itchy Rash: New Study Explains.