Why your run is harder in pollen season

Running during pollen season doesn't just feel harder — it genuinely is. A typical run exposes your lungs to roughly ten times more pollen than a walk covering the same distance.

Here's why. At rest, you breathe around 6–8 litres of air per minute through your nose, which acts as a remarkable filter — trapping and clearing most airborne particles before they travel further. Push into a steady run and that figure jumps to 50–100 litres per minute. At that intensity, your nose can't keep up, so you shift to mouth-breathing, bypassing the nasal filter entirely. Studies estimate this allows 20–50% more pollen particles to reach the bronchi, where they trigger mast cell responses and airway inflammation in sensitised runners. Each 10 grains/m³ increase in ambient pollen raises lower respiratory symptom risk by around 2% — a small number that compounds quickly when you're inhaling at full pace for an hour.

The paradox worth knowing: long-term aerobic exercise actually improves allergic rhinitis symptoms overall. The acute exposure cost is real, but abandoning training isn't the answer.

Instead, time your runs smarter. Pollen counts are typically lowest in late afternoon and early evening, after rain has washed grains from the air, and along coastal or riverside routes where onshore breezes dilute land-based counts. Take a non-sedating antihistamine 2–3 hours before you head out — early enough for peak blood levels to coincide with your run. When you're back, shower and change straight away rather than sitting in pollen-covered kit.

These small adjustments won't eliminate the exposure, but they narrow the gap considerably — and keep your training block intact through peak season.

If you have asthma alongside hayfever, check with your GP before adjusting run timing or medication.