Prevalence of childhood asthma in the tropics.

There is evidence that until quite recently asthma was infrequent in tropical developing countries. Estimates of the current and lifetime prevalence of wheeze and asthma in children in tropical countries in the 1990s suggest that the problem is increasing. There is also evidence that urbanization in tropical areas is associated with a higher prevalence of exercise-induced bronchospasm. Possible contributors to this changing pattern of asthma are discussed. These probably relate to differential exposure to house dust mite and infectious agents in infancy. There is little research on this increasing problem but it is needed in order to find ways to arrest increases in asthma.