Why do I get itchy legs after running?

The itch that ambushes you ten minutes into a run is your skin reacting to the workout's own conditions. Running raises skin temperature, starts sweat, and opens blood vessels in the legs; the NHS lists hot, sweaty skin from exercise among the triggers for hives and itch. In most runners the reaction stays at itch rather than welts - warmth and sweat irritate the skin surface, and in people prone to it, histamine releases produce the prickling, must-scratch feeling across the thighs and calves. Dry skin raises the odds considerably: skin that is already parched (winter air, hot showers, central heating) has a weaker barrier, and sweat salts sting it further - which is why runner's itch often peaks in January and after a layoff, when both the skin and the circulation are out of practice. The fix list is practical: shower lukewarm rather than hot and moisturise daily, especially the legs; wear light, breathable kit that moves sweat away; ease into the pace over ten minutes so the heat rises gradually; and stay consistent - regular runners report the itch fading as their skin and circulation adapt, while the every-three-weeks runner re-triggers it each time. An antihistamine before a run, on a pharmacist's advice, helps stubborn cases. The check-worthy versions: itch that comes with raised welts or hives that spread, itch with lip or face swelling, wheeze, or dizziness during exercise (urgent - that is an allergic pattern), or itchy legs with no clear link to exercise that persists for weeks, which deserves a GP look at skin and general causes. Pymander is a free AI doctor, 24/7 by text, that can help you pin yours down.