Precipitating Factors in Asthma
The identification of precipitating factors that cause asthma exacerbations are critical steps in controlling asthma.

Avoidance of Indoor Allergens: Among the wide variety of allergens that occur within human dwellings are domestic mites, animal allergens, cockroach allergen, and fungi.

Domestic mites: Reducing mites populations is a difficult task. Most attention should be directed to the patient's bedroom although the whole apartment or house should be treated. Mattresses, box springs, and pillows should be encased to deprive mites of an external source of humidity and food. Bed linens should be washed regularly in hot water to ensure mite eradication. The carpet should be removed and replaced by vinyl or polish wooden floor boards, or covered by polyethylene sheeting. Vacuum cleaning remove loose dust but has minimal effect on the number of live mites in the carpet. Children's soft toys can be a potent source of domestic mite allergen and either should be removed or washed in hot water or deep frozen once a week. Acaricides, products that kill mites, are being used but has no proven effect at present. Long term exposure to acaricides is generally not recommended.

Cockroach allergens: Cockroaches are controlled by regular thorough cleaning of infested houses and by the use of pesticides.

Fungi: The number of fungal spores can be best reduced by removing or cleaning mold-laden objects. Maintaining a low humidity is important. Using a dehumidifier and cleaning the unit frequently can significantly reduce mold and bacteria. In addition, air conditioning not only reduces humidity and filters large fungal spores but also effectively lowers the mold and yeast count indoors.

Avoidance of Indoor Air pollutants:The most important measure is to refrain from passive and active smoking. Passive smoking increases the frequency and severity of respiratory symptoms. Parents of children with asthma should be advised not to smoke and not to allow smoking in rooms their children use.
Other major indoor air pollutants are respirable particles like carbon monoxide, sulfur dioxide, formaldehyde, nitrogen oxides, etc. Control of indoor pollutants are expensive and time consuming. It is advised that all gas appliances must have sufficient flues or ducts. Adequate ventilation is necessary to decrease carbon dioxide concentration. Avoiding wood smoke, household sprays, and volatile organic compounds is also important.