Are asthma and allergies increasing in children and adolescents?

Asthma and allergies are the most common chronic diseases in childhood and adolescence with a tremendous impact on life quality and health systems. After the Second World War, an increasing prevalence of allergies and asthma could be observed in westernized countries, while infant mortality and severe infections like tuberculosis were decreasing. This observation turned out to be due to a real increase of diseases, although there was also increased awareness in terms of allergies and asthma. Genes play a major role in the development of the allergic inflammation; however, as genes do not change within a short period of time, the penetrance or expression of genes may have changed due to an altered environment. These factors are thought to be a lack of microbial burden, a decrease in family size, a lack of physical exercise and a change in nutrition. While the increase was very high during the period of 1960 and 1998, a certain plateau has been reached in Central Europe and the US. However, studies like ISAACIII show that in certain regions of the world like Thailand and Lithuania, allergies are still increasing, while low prevalence is observed in rural China.

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