Asthma is a clinical syndrome characterised by often intermittent wheeze due to airway obstruction and inflammation.

Atopy refers to the allergic disposition of an individual. In many large epidemiological surveys, a positive (>3mm) wheal response to one of a battery of allergenic substances on skin prick testing is used to classify a child as atopic.

The review by Pearce et al suggests that the proportion of child asthma cases due to atopy is less than half at the population level.