Insects as allergen injectants, severe reactions to bites and stings of arthropods.

Arthropods capable of penetrating human skin often cause severe local and systemic reactions. Local reactions suggest delayed hypersensitivity while systemic symptoms resemble more the anaphylactic shock in animals. The nature of the antigen remains obscure but predominant evidence suggests its presence throughout the entire organism. Positive history of hypersensitivity to insect injectants was obtained in approximately 20 per cent of persons in the course of routine interviews of 1,078 patients. Repeated bites and stings at long or irregular intervals often induce a state of hypersensitivity, while repeated regular injections of extracts of these insects at shorter intervals may greatly reduce the hypersensitivity. The clinical evidence of allergic sensitivity to insect bites and stings cannot be readily confirmed by skin testing or by other immunological procedures. The history and the character of the lesions as well as certain entomological knowledge of the habits of the insects offer a better basis for specific diagnosis. Treatment with extracts of the whole offending insect generally provides good results but the protection afforded by such treatment varies in degree and duration.