Asthma is a respiratory condition which is most common in young children, causing the lungs to be inflamed and more sensitive. It can be aggravated by exercise, allergies, smoking and infections.
Sufferers can experience asthma attacks when the muscles of the air passage spasm and the lining of the airway swells. As a result, the airway tightens – making it very difficult to breathe.
For more details see the asthma advice sheet.