A summary of our understanding of the complex interactions between chemicals, the immune system, and target organs that lead to manifestations of allergic hypersensitivity and autoimmunity. It concentrates on what is known about the mechanisms of sensitization and autoimmunity elicited by various industrial chemicals, adjuvant environmental factors, such as air pollution, tobacco smoke, and ultraviolet radiation, and food allergens with a proven involvement of the immune system. Over 1000 references to the literature are included. The book opens with an explanation of the structure and functional processes of the immune system, followed by a discussion of the mechanisms by which chemicals can disrupt these functions. Chapter Two provides an overview of mechanisms involved in four major types of hypersensitivity and in autoimmunity. Mechanisms are illustrated with examples of diseases. Factors influencing allergenicity are covered in the third chapter, which concentrates on the many complex endogenous and exogenous factors that govern the induction of allergic responses. The next chapter discusses clinical aspects of the most important allergic diseases, and the remaining chapters review the epidemiology of asthma and allergic disease, including trends over time in different geographical regions. The book concludes with a glossary of terms, followed by 15 precise recommendations for the protection of human health and a list of priorities for further research.