Asthma can be defined as a breathing condition which causes wheeze and cough and where symptoms and breathing tests vary over time. Childhood asthma is a common condition which is thought to affect more than a million children in the UK and many more world-wide. Asthma can differ from child to child, for example many children have mild symptoms for most of the time whereas some usually have more troublesome symptoms. Some children grow out of their asthma but others develop asthma which persists into adulthood. Some children's asthma responds to different medications. The cause(s) of asthma are increasingly better understood and genetic and environmental factors are both important. The reason why asthma is such a variable condition is less well studied; genetic and environmental factors are likely to be important.

Recruiting took place at 15 centres across Scotland between 2008 and 2010 as shown below. 1=Inverness, 2=Elgin, 3=Aberdeen, 4=Dundee, 5=Perth, 6=Stirling, 7=Kirkcaldy, 8=Paisley, 9/10 =Glasgow, 11=Wishaw, 12=Edinburgh, 13=Kilmarnock, 14=Melrose, 15=Dumfries