This thesis focuses on asthma symptoms in early childhood. From a public health perspective, we aim to improve health and health-related quality of life through the prevention of asthma symptoms and by signaling, counselling or management of children who are at a high risk of developing asthma. The public health approach that we used in this thesis provides a useful framework to study the association between social indicators and asthma symptoms in early childhood and the underlying pathways. This thesis also studies the impact of asthma on the child’s health-related quality of life and evaluates the systematic assessment of asthma symptoms and environmental tobacco smoke exposure at preventive youth healthcare centers. Finally, we developed an asthma risk appraisal tool to assess the risk on asthma at school age in preschool children who present with asthma symptoms at well-child care.