Chemical respiratory allergy: role of IgE antibody and relevance of route of exposure.

Chemicals are able to cause various forms of allergic disease in susceptible individuals. Among those of greatest importance in the context of occupational disease is chemical respiratory allergy, where allergic sensitization of the respiratory tract is associated with elicitation of rhinitis, asthma and/or other pulmonary symptoms following inhalation exposure to the inducing chemical allergen. Although for some chemical respiratory allergens (including the acid anhydrides) there exists a strong correlation between symptoms and the presence of specific IgE antibody, for other respiratory sensitizers (and notably the diisocyanates) such an association is variable or absent. These data have resulted in speculation about a universal mandatory role for specific IgE antibody in the induction and elicitation of respiratory allergy to chemicals and of the nature of alternative or complementary mechanisms of sensitization. There is debate also regarding the routes through which exposure to relevant chemical allergens may result in the acquisition of respiratory sensitization. Although inhalation exposure is probably the most common and most important route through which allergic sensitization of the respiratory tract is achieved, there is evidence also that respiratory sensitization to chemicals may be acquired also by dermal contact; observations that have important implications for occupational health management. The significance of IgE antibody and dermal exposure in the context of occupational respiratory allergy to chemicals is discussed.