The University of Georgia College of Veterinary Medicine

Georgia Veterinary Scholar Program

Georgia Veterinary Scholar	Faculty Mentor

Dawn Jackson University of Georgia Class of 2004	Dr. Linda Medleau

Determination of threshold concentrations of inhalant allergens for intradermal skin testing in cats

In intradermal skin testing, the threshold concentration of the allergens should be the highest concentration that can be used to which normal individuals do not react. The purpose of this study was to determine the optimal threshold concentrations of 48 allergens for use in feline intradermal skin testing. Thirty clinically healthy cats were sedated with Medetomidine HCl (Domitor ®) 0.08 mg/kg IM and were intradermally tested with 48 allergens. ½ cc syringes were 27G ½” needles were used to inject 0.05 ml of each allergen intradermally in the following concentrations: 1000 PNU/ml, 2000 PNU/ml, 3000 PNU/ml, and 4000 PNU/ml. Skin test sites were evaluated 15 and 30 minutes post-injection. Positive reactions were recorded if the diameter of erythema or wheal formation for an allergen was equal to or greater than the mean diameter between the negative control (saline) and positive control (histamine). For the purpose of this study, the threshold concentration was defined to be the highest concentration at which one or less of the cats had positive reactions. There were no positive reactions in any of the cats to 25/26 pollens, 8/8 molds, 5/5 danders, and 2/6 insects (cockroaches). For rough pigweed (pollen) one cat had a positive reaction at 2000 PNU/ml, and two cats had positive reactions at 3000 PNU/ml and 4000 PNU/ml. For house dust mites 1 and 2, storage mite, and 4/6 insects, more than one cat showed positive reactions at all concentrations. These results suggest that the threshold concentration for rough pigweed is 2000 PNU/ml and for all of the molds, danders, cockroaches, and 25/26 of the pollens it is above 4000 PNU/ml. Further investigation using lower concentrations of house dust mites 1 and 2, storage mites, and 4/6 of the insects is needed to determine their threshold concentrations.