Asthma is a common and potentially serious chronic disease affecting the airways that imposes a substantial burden on patients, their families and the community. It affects people of all ages and often starts in childhood, although it can also develop for the first time in adults.

It involves inflammation and narrowing of the airways (bronchi), which restricts air supply. It causes respiratory symptoms, limitation of activity, and flare-ups (attacks) that sometimes require urgent health care and in rare cases may be fatal. It is characterised by variable symptoms of wheeze, shortness of breath, chest tightness and cough that vary over time and in intensity, together with variable airflow limitation that is often reversible either spontaneously or with the treatment.

Symptoms may occur several times in a day or week in affected individuals, and for some people become worse during physical activity or at night.

Factors that may trigger or worsen asthma symptoms include viral infections, domestic or occupational allergens (e.g., house dust mite, pollens, cockroach), tobacco smoke, exercise, certain drugs (e.g. aspirin or other nonsteroidal anti-inflammatory drugs) and stress.

An appropriate diagnosis, based on the medical history, symptomatology and evidence of airflow limitation, allows early intervention for a better disease control and good quality of life.