Allergens

Dust or house mites, molds, pollen, animal dander, cockroach feces, pets, and feathers

Exercise

Particularly exercise in cold or dry air

Irritants

Firsthand and secondhand tobacco smoke, perfumes, wood smoke, cleaning products, scented candles, air pollution, strong odors, and irritating fumes

Viral respiratory infections*

In young children: Respiratory syncytial virus, rhinovirus, parainfluenza virus infection

In older children: Upper respiratory infections (particularly with rhinovirus) and pneumonia

Other

Emotions (such as anxiety, anger, and excitement)

Aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs)

Gastroesophageal reflux