Dust or house mites, molds, outdoor pollen, animal dander, cockroach feces, and feathers
Particularly exercise in cold or dry air
Firsthand and secondhand tobacco smoke, perfumes, wood smoke, cleaning products, scented candles, outdoor air pollution, strong odors, and irritating fumes
Viral respiratory infections*
Respiratory syncytial virus Respiratory Syncytial Virus (RSV) Infection and Human Metapneumovirus Infection , rhinovirus Common Cold , parainfluenza virus infection
* Viral infections are the most common triggers in children.