A number of factors can trigger asthma, most often by causing a bronchospasm (narrowing of the airways) and inflammation (redness and swelling). Environmental factors are among the most common causes. Air quality therefore has an important effect on asthma.

Our lungs interact continuously with surrounding air. Asthmatic airways have an exaggerated reaction to airborne dust and particles.

Asthma may therefore be affected by the quality of air inside and outside of the home.

This section examines a number of factors that can trigger asthma. These factors are divided into those that cause inflammation (the most important), respiratory irritants and other factors.

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Inflammatory factors cause airway inflammation (swollen) and can prolong asthma symptoms for weeks or months, depending on the length of exposure. Control of these factors should be a priority. The greater the degree of airway (bronchi) inflammation, the more sensitive lungs are to respiratory irritants, cold air or exercise.

Airway inflammation may be caused by, or worsen following, exposure to substances the asthmatic person is allergic to, such as animal dander, house dust mites, pollen, molds or sometimes respiratory infections.

Substances in the workplace can also cause bronchial inflammation or asthma.

Irritants produce short-term symptoms. Although people are usually not allergic to them, they can still be bothersome. These symptoms are caused by contraction (squeezing) of airway muscles leading to narrowing of the airways (bronchospasm). Inflamed airways are more sensitive to respiratory irritants.

Respiratory irritants include tobacco smoke or strong odours from household products, solvents, aerosols or perfumes.

Tobacco smoke is a major respiratory irritant that aggravates airway inflammation. It is therefore important not to smoke and to avoid second-hand smoke. Exposure to fireplace smoke pollutants and other irritants can make it difficult to control asthma.

Exercise, cold weather or temperature changes can also cause bronchial constriction. It is essential, however, that asthmatics remain physically active. If your tolerance to physical exertion decreases, it is a sign that your asthma is not well controlled. Discuss this with your physician.

Reducing the factors that trigger an asthma attack, or eliminating them altogether, can help minimize your asthma symptoms.

People who are severely asthmatic should avoid contact with irritants to minimize symptoms.