Scratching a bug bite or rash is common, but researchers have found that it can worsen the itch and delay healing. While scratching is a natural response to skin irritants, it increases skin inflammation and can aggravate conditions like eczema.
A research team from the University of Pittsburgh, led by Professor Daniel H. Kaplan, explored why scratching exacerbates swelling and its evolutionary significance. They noted this area was “poorly explored.” In their study, they applied an allergen to the ears of mice to induce allergic-contact dermatitis, a skin condition similar to eczema. The resulting reaction mimicked what humans experience with allergens like poison ivy and certain metals.
The study involved two groups of mice: one “normal” and another genetically modified to lack an itch-sensing neuron. Some mice could scratch freely, while others wore collars to prevent it. The findings showed that scratching activated mast cells, described by the Cleveland Clinic as part of the body’s “alarm system,” releasing chemicals that enhance itchiness.
Scratching causes the release of substance P, a molecule that activates more mast cells, leading to increased inflammation and an itch-scratch cycle. Mice prevented from scratching experienced less inflammation. During bug-bite season, researchers urge against scratching, which worsens inflammation.
Science has reported that the ability to feel itch and scratch is an evolutionary trait, developed millions of years ago. Mast cells play a vital role in defending against bacteria and pathogens. The researchers conducted further experiments to see if scratching impacts the skin’s microbiome. They found that scratching reduced levels of Staphylococcus aureus, a bacterium linked to skin infections.
Despite scratching offering bacterial defense, the skin damage from chronic itching outweighs this benefit. Cold compresses and 1% hydrocortisone cream are suggested for itch relief, according to the American Academy of Dermatology.
This research was published in the journal Science. Teresa Mull, a freelance writer with the Fox News Digital Lifestyle team, contributed to this report.
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