The objective of the evidence-based guidelines 'Asthma in children (ages 0-19)' for youth healthcare (CHC) is the prevention and reduction of asthma symptoms. The guidelines contain a lot of recommendations that apply to all disciplines in healthcare that deal with children. Primary prevention (preventing asthma): the main proven effective intervention is no smoking, neither passive nor active. Breastfeeding has a small protective effect. Starting at the first home visit at two weeks, the CHC nurse advises no smoking and to breastfeed. Secondary prevention (early detection): at all routine check-ups, the professional at CHC should inquire about signs of dyspnoea and wheezing. Patients suspected of having asthma should be referred to the GP. Tertiary prevention (reducing symptoms in children with asthma): the main advice is no smoking (neither passive nor active) and to follow the advice of the treating physician.