Study finds scratching insect bites prolongs itching through nerve cell pathway

Pittsburgh — Research led by dermatologist Dr. Daniel Kaplan at the University of Pittsburgh has identified a cellular mechanism explaining why scratching insect bites extends the itch. In experiments on mice with allergic reactions, rodents fitted with protective collars resembling veterinary "cones of shame" — preventing them from scratching — showed markedly less swelling and inflammation than those allowed to scratch freely. Dr. Kaplan said similar effects occur in humans, noting that an undisturbed mosquito bite typically fades within about 10 minutes, while scratching causes swelling to intensify and persist for roughly a week. The findings were reported by ABC News. The research found that scratching continues until pain sets in, triggering nerve cells to release a chemical messenger called Substance P. That substance activates mast cells through a newly identified molecular pathway, increasing the release of inflammation-triggering compounds and reigniting the itch. To ease itching, specialists recommend hydrocortisone cream, calamine lotion and oatmeal baths. Mentol-based creams were also cited as potentially helpful by creating a cooling sensation that can interrupt the scratch-itch cycle, though researchers cautioned the relief is temporary.