Allergens

• Pollen (trees, grasses, and weeds)

• Mold

• Pets (cats, dogs, hamsters, and birds)

• Dust and dust mites

• Cockroach droppings

• Mice and other pests

Respiratory infections

• Viral infections, including the common cold

• The flu

• Sore throat

• Sinus infection

Irritants

• Strong odors and sprays, such as perfumes, household cleaners, paints, and varnishes

• Chemicals, such as coal, chalk dust, or talcum powder

• Air pollutants, such as ozone and chemicals in the air

• Weather conditions, including cold or wind, or hot, humid weather

• Chemical exposure on the job, such as dust, gases, or fumes

Sensitivity to medicines and food preservatives

• Aspirin

• Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen

• Sulfites used as preservatives in foods and drinks

Exercise

• Strenuous physical exercise 

• Long-term activities, such as long-distance running

Other conditions

• Gastroesophageal reflux disease (GERD)

• Higher weight

• Obstructive sleep apnea

Smoke

• Tobacco smoke, both inhaled and secondhand

• Smoke from wood-burning stoves and fireplaces

• E-cigarettes

Emotions

• Anxiety

• Stress

• Depression

• Anger