A runny nose during exercise is extremely common and usually harmless. Known as exercise-induced rhinitis, it affects more than half of people who work out, whether they have allergies or not. The clear, watery drip you’re wiping away mid-run or between sets is your nasal passages responding to increased airflow, temperature changes, and shifts in how your nervous system regulates blood flow to the nose.
What Causes It
When you exercise, your breathing rate increases dramatically. You pull in far more air through your nose and mouth than you do at rest, and your nasal passages have to work harder to warm, humidify, and filter that air. This rapid conditioning of large volumes of air draws moisture from the lining of your nose, triggering it to produce more mucus to compensate.
Your nervous system also plays a direct role. At rest, sympathetic nerves keep the blood vessels in your nasal lining in a relatively constricted state. During intense physical activity, shifts in this nerve signaling can reduce that constriction, allowing blood vessels in the nose to widen. When those vessels open up, fluid seeps into the surrounding tissue and the nasal lining swells, producing that familiar drip. This is less about your body overreacting and more about a normal fluctuation in how your nervous system manages blood flow during exertion.
Cold, dry air makes everything worse. When you breathe in air that’s both cold and low in humidity, the evaporative water loss from your airway surface increases significantly. That dehydration triggers the release of inflammatory chemicals, including histamine, which increase vascular permeability (essentially making blood vessels leakier) and stimulate mucus glands. This is why winter runs and cold-weather sports are especially notorious for producing a streaming nose.
Allergies vs. Non-Allergic Exercise Rhinitis
If you already have nasal allergies, exercise will likely make your symptoms more noticeable. In one study, about 72% of people with nasal allergies reported rhinitis during outdoor exercise, compared to 41% of those without allergies. But plenty of people with no allergy history at all get a runny nose when they work out. The key difference: allergic rhinitis typically comes with itchy eyes, an itchy nose, and sneezing, while non-allergic exercise-induced rhinitis is mostly just a runny or stuffy nose without the itch.
If your symptoms happen only when you exercise outdoors during pollen season, allergies are likely amplifying the problem. If your nose runs just as much on the treadmill in January, the trigger is almost certainly the exercise itself.
How Your Workout Environment Matters
Where you exercise can change the type and severity of nasal symptoms you experience. Competitive swimmers, for instance, deal with a distinct pattern. While the overall rate of exercise-induced rhinitis is similar between swimmers and runners (roughly 21% to 23%), swimmers tend to experience worsening nasal function after training rather than just during it. Chronic exposure to chlorine and its byproducts in pool air irritates the nasal lining, leading to more congestion, sneezing, itching, and postnasal drip compared to land-based athletes. This holds true regardless of whether the swimmer has allergies.
Indoor gyms with poor ventilation, dusty environments, and areas with strong cleaning chemical odors can also aggravate symptoms. Outdoor exercise in cold weather remains one of the strongest triggers because of the combined effect of cold and dry air on the nasal lining.
When It Becomes a Bigger Problem
For most people, exercise-induced rhinitis is an annoyance, not a health concern. Your nose runs, you wipe it, you keep going. But athletes who train intensively over long periods can develop more persistent issues. Frequent high-intensity exercise is associated with nasal epithelial injury (damage to the cells lining the nose), increased inflammatory cell activity, and decreased mucociliary clearance, which is your nose’s ability to sweep irritants and mucus out efficiently. Over time, these changes can contribute to chronic sinus problems and interfere with athletic performance.
This is primarily a concern for competitive or endurance athletes logging heavy training hours, especially in cold weather or chlorinated pool environments. If you’re exercising a few times a week at moderate intensity, chronic complications are unlikely.
Practical Ways to Reduce Symptoms
A few simple adjustments can make a noticeable difference:
- Warm up gradually. A slow warm-up gives your nasal passages time to adjust to increased airflow rather than being hit with a sudden surge.
- Cover your nose in cold weather. A buff, balaclava, or even a loose scarf over your nose and mouth warms and humidifies the air before it reaches your nasal lining, reducing the dehydration response.
- Breathe through your nose when possible. Nasal breathing warms and filters air more effectively than mouth breathing, though this becomes harder at higher intensities.
- Choose your environment. If you have the option, exercising in warm, humid conditions produces fewer nasal symptoms than cold, dry air. Moving a winter run indoors can help.
- Rinse after swimming. A saline nasal rinse after pool sessions helps flush chlorine byproducts from the nasal lining before they cause prolonged irritation.
If environmental changes aren’t enough, a prescription nasal spray that blocks the nerve signals responsible for mucus production can be effective. This type of anticholinergic spray is used before exercise to reduce the watery discharge. An over-the-counter saline spray or a nasal steroid spray may also help, particularly if underlying inflammation or mild allergies are contributing. If your symptoms are persistent and bothersome enough to affect your workouts, it’s worth bringing up with your doctor, since the right nasal spray used before exercise can make a significant difference.