Asthma is a disease of the lungs and of the air tubes leading to them. The bands of muscle around the outside of the bronchioles tighten, further blocking the flow of air. No one is sure what causes asthma, but the bronchioles of many people who have asthma are more sensitive than usual to certain triggers. Exercise, especially in cold weather, can trigger asthma in some people, as can emotional factors such as stress or anxiety.
Asthma runs in families to some extent.
It is particularly common in children, although about half of all children with asthma outgrow it by the age of 15 years. However, asthma can can recur in adult life and it can begin at any age. It is becoming more common in the UK and many other countries, but no one is sure of the reasons for this. Asthma causes recurrent episodes of shortness of breath, wheezing, coughing and a feeling of tightness in the chest. Often, especially in young children, the only symptom is a cough, which is sometimes present only at night.