Why do my legs itch when I run?

“Every time I try to go running, my legs itch really badly. Is something wrong?”

We’re neither doctors nor physical trainers here at the library, but we looked into it. Itchy legs during exercise are common enough that Go Ask Alice, Livestrong, and Outside all covered the problem on their websites.

If the itching is accompanied by hives and difficulty breathing, it may be a symptom of exercise-induced anaphylaxis, a serious, though very rare, condition, and you should visit your doctor. If it’s only the hives, they can be triggered by a multitude of things, including the increased body temperature that comes along with hot weather, stress, or exercise. (Another term for hives is “urticaria,” and the specific type that’s triggered by exercise is “cholinergic urticaria.”)

The season could also be the culprit. Skin can get dry and itchy in the winter, and may be further irritated by sweat and tight-fitting clothes. Some people also have cold urticaria, a condition where, as the name suggests, cold temperatures bring on hives.

According to another theory, the itching is caused by blood moving through your capillaries. The capillaries expand during exercise to increase blood flow, and if your body isn’t used to that, nearby nerves send signals to the brain that it interprets as an itching feeling. Go Ask Alice and Livestrong both support this theory, though Outside argues that there isn’t enough evidence.

To control the itching, try wearing loose cotton clothes, as tight synthetic material can aggravate sensitive skin. Make sure your skin is well-moisturized and that you’re dressed for the weather. Outside and Livestrong also suggest taking an antihistamine before exercising. Finally, keep at it – as your body gets used to the workout, the itching sensation may diminish in time.

Runners looking to improve are welcome to come check out our selection of books, including Build Your Running Body by Pete Magill, Thomas Schwartz, and Melissa Breyer; Runner’s World Complete Book of Running; Running: Start to Finish by John Stanton; and Feet, Don’t Fail Me Now by Ben Kaplan.