However, as stated above, it may be that childhood asthma differs from that in adults. It seems that relatively poorly controlled asthma in children who exhibit frequent symptoms do not necessarily show abnormal lung function between their periods of symptoms. It is for this reason that in our study we will be concentrating on outcome measures such as exacerbations and quality of life although we will have the opportunity to measure spirometric values at the first (T0) and last (T48) visits in the randomised part of the study. It could be that an increase in medication may only be needed for a short time in children with asthma and there have been suggestions that once control is achieved children should have their add-on therapy reviewed. To incorporate such a step within the present study would make it excessively complicated and would have major implications on the number of patients included. The inclusion of such a step would make the study impractical within the UK. A study is needed which is simple, pragmatic (but placebo-controlled and double-blinded), has outcomes which will be of practical benefit to children and will provide evidence for the use of add-on medications in the most cost effective and efficient way. Children dislike exacerbations. School attendance, daily activity and general well-being increase when asthma is well controlled. Once families understand sufficiently about asthma, inhaler technique has been evaluated and optimised, and compliance issues addressed, one of the reasons why a specific medication may be less effective could be related to the genetic make-up of the patient. In this study we will have the opportunity, through a separate consent process, to collect and store DNA specimens from saliva for later analysis of specific genetic polymorphisms in relation to asthma severity and outcome. This aspect will bring added value to the study.