At previous study visits that occurred when participants were 1, 2, 4, and 10 years old, information on the following was collected: asthma and other allergic diseases, family history of asthma, and early life risk factors, including breastfeeding and tobacco smoke exposure. A blood sample was collected at participants' 10-year study visit. For this current study, all 18-year-old participants will return for a study visit. Participants will complete questionnaires on asthma and allergy symptoms and environmental exposures, including tobacco smoke and pollution. Blood collection, an allergy skin prick test, lung function testing, and a bronchial challenge test to assess airway function will occur. Select participants will also have a sputum sample collected.