Asthma is the most common chronic disease in childhood. It is defined as a chronic inflammatory disorder of the airways in which many cells and cellular elements promote airway obstruction and hyper-responsiveness (GINA, 2012). According to the World Health Organization (WHO, 2014), asthma is estimated to affect approximately 253 million people worldwide. Despite advances in biological and pathological research, the prevalence of asthma in children has significantly increased over the past decade (Massingham et al., 2014).