Cutaneous histamine reactivity, histamine content of commercial allergens, and potential for false-positive skin test reactions in dogs

Abstract

Summary The cutaneous reactivity of normal and atopic dogs to intradermal injections of histamine phosphate was evaluated. Significant differences were not found in the mean wheal diameters of either group. Commercial allergens used for intradermal skin testing and immunotherapy were determined to contain histamine. To determine whether allergen histamine content was sufficient to cause false-positive skin test results, the cutaneous response of Johnson grass allergic dogs was compared, using commercial Johnson grass allergen and commercial Johnson grass allergen with histamine removed. Significant differences were not noticed between Johnson grass and dehistaminized Johnson grass. Therefore, the histamine content of commercial Johnson grass allergen did not appear to cause false-positive skin test results for this group of Johnson grass allergic dogs.