Asthma is the most common chronic disease in childhood characterized by chronic bronchial inflammation of variable intensity accompanied by spontaneous or drug reversible airflow obstruction. The onset of asthma, clinical presentation and response to therapy are influenced by numerous genetic and environmental factors. Asthma in childhood is characterized by its heterogeneity in terms of possible etiology, degree of inflammation and airway obstruction, lung function as well as the natural course of disease that may persist and continue to adulthood. Protective factors linked to early life experiences have also been delineated which may impact the development of asthma. Pathophysiological mechanisms of allergic reaction as an excessive inflammation driven by T-helper-2 (Th2) immunity, offer poor understanding of the heterogeneity of clinical disease. A recently introduced approach defines asthma as a syndrome that comprises of several subtypes or endotypes based on entirely novel pathways to disease. Timely diagnosis and adequate treatment are necessary to prevent irreversible airway remodeling and consequent decrease in pulmonary function.