Asthma is a chronic inflammatory condition of the airways that causes episodic exacerbations of  bronchoconstriction secondary to T1 hypersensitivity.

Epidemiology

It affects over 10% of children and around 5-10% of adults, with the prevalence of asthma increasing. Not only does asthma account for a significant morbidity burden it should be remembered that around 1,000 people die in a year from asthma in the UK, 30-40 of whom are children.

Risk factors and aetiologies

A number of factors can increase the risk of a person developing asthma:

• personal or family history of atopy (eczema, hay fever)
• antenatal factors: maternal smoking, viral infection during pregnancy (especially RSV)
• low birth weight
• not being breastfed
• maternal smoking around child
• exposure to high concentrations of allergens (e.g. house dust mite)
• air pollution
• Occupational asthma - Isocyanates are the most common cause, also flour
• 'hygiene hypothesis': studies show an increased risk of asthma and other allergic conditions in developed countries. Reduced exposure to infectious agents in childhood prevents normal development of the immune system resulting in a Th2 predominant response
• A number of patients with asthma are sensitive to aspirin

Typical Triggers

• Infection