Figure 1.

Example of the limited intradermal test (IDT). Saline (Greer Laboratories) and histamine 0.1 mg/ml (Histatrol; ALK) were used as the known negative and positive controls (top row). The cat was injected with 0.1 mg/ml of histamine, 0.05 mg/ml of histamine, saline, 8000 protein nitrogen units (PNU)/ml) of Schinus species (Pepper tree; Greer Laboratories) and 8000 PNU/ml of Cynodon dactylon (Bermuda grass; Greer Laboratories). Each of the five items were duplicated and injection sites randomized for each cat with the investigator blinded (middle and bottom rows). A total of 0.05 ml was delivered for each intradermal injection via a 27 G needle. The IDT was read 15 mins after the first injection. A subjective wheal score of 0–4 was given to each wheal based on erythema, size, turgor and steepness of the wheal. An objective wheal score was determined by measuring the longest and shortest diameter of the wheal