Environmental effects on immune system and allergy.

Incidence and severity of allergic diseases of the upper and lower airwys has been increasing throughout this century. The hallmark of these disorders is increased IgE production. Many epoidemiological studies have provided indirect evidence for an increased incidence of asthma and atopy linked to airborne pollution in developed countries. In order to better understand the complex interaction(s) between pollution and allergic diseases, we suggest to consider four fundamentl mechanisms. 1. Increased concentration of airborne allergens in urban areas and workplaces. 2) Adjuvant effect. 3) Xenobiotic interaction(s) with immune system. 4) Effects of pollutants on target organs. In conclusion, although epidemiological and laboratory studies show contrasting results, there is evidence that xenobiotics are involved in the pathogenesis of allergic diseases through specific and non-specific mechanisms.