The use of compound 48/80 and codeine phosphate as positive controls for intradermal skin testing in dogs

The mast cell secretagogues compound 48/80 and codeine phosphate were evaluated as potential positive controls for intradermal skin testing in dogs. Wheal responses to both agents were compared with responses to histamine and saline in 11 normal dogs, and were strong and not significantly different from histamine responses in nine dogs (P < 0.01), and significantly weaker than histamine in two dogs (P < 0.05). Wheal responses to compound 48/80 (1 mg mL-1) were evaluated in 82 suspected atopic dogs and were similar to histamine in 79 dogs and markedly weaker than histamine in three dogs. Of nine confirmed atopic dogs with weak responses to injected allergens, seven had strong responses to compound 48/80, and eight had strong responses to histamine. Compound 48/80 and codeine phosphate appear unreliable positive controls for skin testing in normal dogs. Compound 48/80 (1 mg mL-1) may be a reliable positive control in atopic dogs but is a poor indicator of skin reactivity to allergens.