[Air pollution and allergic asthma].

The prevalence of asthma and allergic diseases is increasing in all industrialized countries. Genetic and environmental factors, and their interactions, are responsible for this increasing prevalence. A certain number of genes are currently screened to determine their suspected role in the immunogenesis of asthma, but in themselves, they cannot explain the increasing prevalence of asthma observed over the last 20 years. Environmental factors appear to be the most plausible explanation. Among these factors, air pollution and changing lifestyle as well as lower resistance due to fewer infectious diseases during childhood may be the most important factors. Experimental studies have shown that some pollutants such as ozone or diesel exhaust particles can interact with allergens, amplifying allergic reactions. Epidemiological studies have provided contradictory results. Acutely high concentrations of different pollutants can induce transient respiratory symptoms in asthmatic subjects but the long-term effects of air pollution on the genesis of asthma are still quite unclear.