Comparison of rat fur, urine, saliva, and other rat allergen extracts by skin testing, RAST, and RAST inhibition.

Extracts of a wide range of materials associated with exposure to rats were prepared and their relative allergenic activities were measured by skin-prick testing of rat-sensitive patients, RAST for serum IgE, and RAST inhibition of dust collected from a rat room. Most potent on a dry weight basis were preparations of fur, urine, epithelia, and saliva (all irrespective of the sex of the rat) and of the dust. Extracts of shaved pelt, whole pelt, feces, and serum proved less effective, whereas those of sawdust or diet had negligible activity. The presence of similar allergens in the more potent extracts was suggested by multiple skin sensitivity to different source materials, by close correlation between RAST results, and by the extent of RAST inhibition for individual extracts. The allergenicity of fur and epithelia probably results largely from contamination with saliva and urine.