The Real Reason Your Legs Itch When You Go On A Run

It's a good thing that every now and then, we get that runner's high — an endorphin-triggered feeling of euphoria that blesses us the luckiest among us during a run (via Runner's World). Because so many other times, running is a comedy of errors, is it not? The cramp, the bad knee, the untied shoelace, the playlist that keeps skipping, the unexpected rain, or that cyclist who almost ran you off the sidewalk. But here's a running hassle you might not have been expecting: itchy legs. What, did you run into a swarm of mosquitoes, on top of everything else?

Nah, it's just the capillaries in your legs expanding because your heart rate is increasing; the nerves surrounding the capillaries send messages to the brain, which reads this as itching (via PopSugar). "If you think of the blood vessels in your muscles like city roads, when you start to run, you're going to have more traffic on the road — it's going to get congested," Geoff Burns, Ph.D., a researcher at the Michigan Performance Research Laboratory at the University of Michigan and competitive ultrarunner, explained to SELF. "These vessels aren't mechanically used to expanding like that, and that might put pressure on some of the nerve tissue in the muscles or other mechanoreceptors there. That can give you that itchy sensation."

Less experienced runners are most likely to get itchy legs

According to Burns, itchy legs during running is more likely to happen when someone is either new to running, or hasn't run in a long time. "One of your body's initial responses to running if you've never done it before is called vasodilation, where your blood vessels open up or expand to let more [blood] come through," he explained. After a few weeks of running, this itchiness should stop, Burns added.

If this situation doesn't sound like you — maybe you're no running novice, and are even an ultrarunner like Burns — you could be getting itchy legs for another reason. It might be a heat rash, which is most likely to occur when you've run in hot, muggy weather and is due to a sudden increase in body temperature (per VeryWellFit). Runners who get heat rash also may get a similar sensation when they eat spicy food, or it can even pop up due to emotional stress. If that itchiness is also accompanied by stomach cramps, headache, facial swelling, or diarrhea, stop exercising immediately and contact your doctor; this could be a more serious condition called exercise-induced urticaria (per Family Doctor).