Asthma and migration.

The dramatic influx of immigrants from South-East Asian countries into Australia over the past 20 years was associated with an increase is asthma and allergic disease amongst these immigrants. Epidemiological data showed that the prevalence rates of asthma and allergic disease increased with the duration of residence in Australia so that after 10 years in Australia, up to 60% of South-East Asian immigrants developed hayfever while 15% had symptoms of asthma. Many immigrants developed these conditions for the first time after arrival in Australia suggesting that the environment plays a important role in the pathogenesis of asthma and allergy. While sensitization to inhalant allergens such as house dust mite and grass pollen are apparently important in some, other yet undefined local factors are likely to contribute significantly to the overall increase in prevalence. A prospective study designed to follow a group of migrants in areas where asthma and allergic disease are common such as Australia, may reveal the pathogenic role of the environment and provide valuable information that may explain the global distribution and increasing trend of asthma and allergies.