CUTANEOUS HISTAMINE REACTIVITY, HISTAMINE CONTENT OF COMMERCIAL ALLERGENS, AND POTENTIAL FOR FALSE-POSITIVE SKIN-TEST REACTIONS IN DOGS

The cutaneous reactivity of normal and atopic dogs to intradermal inje ctions of histamine phosphate was evaluated. Significant differences w ere not found in the mean wheal diameters of either group. Commercial allergens used for intradermal skin testing and immunotherapy were det ermined 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 allerge n with histamine removed. Significant differences were not noticed bet ween Johnson grass and dehistaminized Johnson grass. Therefore, the hi stamine content of commercial Johnson grass allergen did not appear to cause false-positive skin test results for this group of Johnson gras s allergic dogs.