Asthma can be described as a condition in which the airways of the lungs become either narrowed or completely blocked, preventing normal breathing. Although everyone's airways have the potential for constricting in response to allergens or irritants, people with asthma have an oversensitive reaction. In response to stimuli, the airways may become obstructed by either a tightening of the muscles surrounding the airway; inflammation and swelling of the airway; or increased mucus production which clogs the airway. After the airways become obstructed, it takes more effort to breath, giving rise to the symptoms of asthma, i.e. wheezing, coughing, tightness around the chest and shortness of breath.

Factors which trigger asthma attacks are usually described as either allergic or non-allergic. Allergic factors include dust, pollen, mould, animal hair and certain food or drinks. Non-allergic factors include exertion, smoky atmosphere, cold, dampness, chest cold and infections. In the majority of cases, asthma is caused by a combination of factors.

Treatment of asthma is by using Preventers and Relievers. Preventers such as inhalers are used regularly even when no systems are present. They are not meant to give rapid relief of wheeze. Very often, a combination of Preventers and Relievers is recommended.