Percutaneous prick test irritant threshold concentrations for eight allergens in healthy nonsedated dogs in the USA

Percutaneous testing (PT) is preferred to intradermal testing in humans for the in vivo identification of allergen hypersensitivity, but the methodology has not been well described for use in dogs with atopic dermatitis.

To identify the irritant threshold concentrations (ITC) of eight aeroallergens using a commercial prick test device in normal dogs.

Twenty healthy, privately owned dogs.

Percutaneous testing was performed using the GREER^® Pick^® System (Stallergenes Greer; Lenoir, NC, USA). Five dilutions of glycerinated extracts of Bromis inermis, Sorghum halepense, Chenopodium album, Ambrosia psilostachya, Salix nigra and Acer negundo, as well as four dilutions of Dermatophagoides farinae and D. pteronyssinus were included. Glycerinated histamine (6 mg/ml) and glycerin/Coca's solution were used for the positive and negative controls, respectively. Orthogonal wheal diameters were measured for each test site every 5 min for 25 min. Reactions were considered significant when the average wheal diameter was equal to or greater than the mean of the positive and negative controls.

Significant reactions were noted in five of 20 (25%) of dogs. The ITC (≤10% of dogs reacting) were 1:20 w/v for B. inermis and S. nigra, 1:400 w/v for D. farinae and 1:200 w/v for D. pteronyssinus.

These results suggest that the pollen allergens evaluated in this study can be used for PT at their undiluted concentration (1:20 w/v) with a reasonable assurance of few false positive reactions in dogs. Dust mites require dilution for testing at the ITC.