Aetiological agents in occupational asthma.

Occupational asthma has become the most prevalent occupational lung disease in developed countries. At present, about 200 agents have been implicated in causing occupational asthma in the workplace. These agents can be divided into two categories by their mechanism of action: immunological and nonimmunological. Immunological causes can be further divided into those that induce asthma through an immunoglobulin E (IgE)-dependent mechanism, and those that induce asthma through a non-IgE-dependent mechanism. In the latter category, specific IgE antibodies are found only in a small percentage of the patients with proven disease, even though the clinical picture is compatible with an allergic reaction. The immunological mechanism(s) responsible for these agents has yet to be identified. The best known example of nonimmunological asthma is Reactive Airways Dysfunction Syndrome (RADS) or irritant-induced asthma. In this review, examples of types of agents causing occupational asthma are discussed and a compendium table of aetiological agents is given.