PhysioWorks News & Tips: What Is That Itch? Running Induced Itchiness Is A Thing!

It's a cool morning and you are 5 minutes into your run. The sun is breaking through the trees, your breath is creating clouds of mist in the air. You're feeling good! But then, building up in your thighs is a distracting widespread itch and redness.

What Is Going On?

This is actually a fairly common phenomenon — known as runner’s itch — and is typically harmless and often more noticeable when returning to exercise after a break.

When you run, your heart pumps harder to supply oxygen-rich blood to your working muscles. This increased blood flow causes small blood vessels (capillaries) to expand, which can stimulate nearby nerve endings in your skin. Your brain interprets this sensation as itching. Exercise may also release histamines, which contributes to blood vessel dilation and further itchiness.

Sensitive skin, certain fabrics, or sweat mixing with detergents can make the problem worse. Thankfully, in most cases, runner’s itch settles as your body adapts.

Surprisingly, you don’t even need traditional exercise to trigger that post-workout itch. A study (Mueller et al, 2018) using whole-body vibration (WBV) where mechanical vibrations activate your muscles found that participants developed itching and skin redness, especially in the thighs and lower legs. The itching usually started first, followed by redness that got more noticeable as the session continued.

Interestingly, the more people’s skin temperature rose, the itchier they felt but this didn’t always match how red their skin looked. And while there was a small drop in a chemical linked to allergic reactions, it stayed within the normal range, suggesting the itch likely wasn’t caused by an allergy, but rather by increased blood flow and nerve stimulation.

So, next time your legs itch during a run, remember it’s just your body adjusting. What's more is that as you get fitter, the itch tends to lessen. But if it becomes intense, persistent, or is accompanied by other symptoms, it’s wise to consult a health professional.