Many children with asthma can achieve symptom and disease control by using inhaled corticosteroid (ICS) therapy combined with a long acting B2 agonist (LABA) and/or a leukotriene receptor antagonist (LTRA) (International ERS/ATS guideline, 2014). However, a number of children with asthma experience frequent symptoms despite being prescribed high dose ICS (Nagakumar and Thomas, 2013; Hedlin et al., 2014).