The use of compound 48/80 as a positive control in equine intradermal allergy testing

The macroscopic and microscopic effects following the intradermal injection of the mast cell degranulator compound 48/80 were investigated in horses. It was found that a 1000 μg mL^-1 solution of compound 48/80 could be used as an alternative to histamine as a positive control in equine intradermal allergy tests. An inflammatory cell infiltration was noted on histological examination, following compound 48/80 injection. This inflammatory cell pattern was similar to that noted for Type-I hypersensitivity.