Environmental factors and respiratory hypersensitivity: experiences from studies in Eastern and Western Europe.

Allergy and respiratory hypersensitivity are the end results of an interaction in genetically susceptible individuals, exposure to allergens and adjuvant factors. The incidence of allergic disease (but not respiratory hypersensitivity) is higher in urban than in rural areas and in Western industrialised countries than in the formerly socialist countries of Eastern Europe. It appears to be caused by factors encountered in early childhood. Tobacco smoke is by far the most important single environmental risk factor that has been identified so far. Other risk factors include air pollution such as NO2, SO2 and ozone, and modern, tightly isolated and poorly ventilated houses. However, even if all known environmental factors are added, this could only partly explain the increasing prevalence of these diseases. Therefore, other, unknown factors associated with 'Western lifestyle' must be looked for.