The diagnosis of asthma will be determined at age 6 years based on responses to the ISAAC questionnaire. [6] [7] [8] The following criteria will define asthma during the sixth year of life: (i) 12-month prevalence of symptoms of asthma (current wheeze) or the presence of exercise-induced wheeze or dry cough at night not due to a cold or chest infection; and (ii) physician diagnosis as determined by the ISAAC questionnaire using either parental reported physician diagnosis of asthma or chronic use/ prescription of asthma-specific medications. Probable asthma will be defined as physician diagnosis only and analysed separately. Transient early wheezing will be defined as wheezing episodes present in the first 4 years of life, but not meeting the definition for childhood asthma at age 4 and 6 years. 29 Allergic rhinitis will be determined through the ISAAC core questions on AR. 7, 8 Children will be considered to have definite AR if each of three conditions is present between age 5 and 6 years: (i) a history of nasal congestion, runny nose, itchy watery eyes, sinus pain or pressure or headaches, sneezing, blocked nose, loss of sense of smell; (ii) substantial variability in symptoms over time or seasonality; and (iii) diagnosed as having allergic rhinitis by a physician or on medications for AR. Probable allergic rhinitis will be defined as meeting two of the three criteria, or only criteria 3.