All 160 veterinarians who had purchased the injectable form of RESPIT® (SkinVet, Lake Oswego, OR, USA) between March 2010 and September 2012 were contacted by mail in June 2013 and asked to review their patients' records. Each aqueous allergen mixture contained 20 house dust mite and regional pollen antigens. Surveys were accepted up to a predetermined deadline of July 31. Veterinarians were asked to complete one survey per dog treated with RESPIT fulfilling defined inclusion criteria, estimating pruritus and lesion severity at Day 1 of RESPIT therapy and again at the time of the most recent follow-up examination.

Fifteen veterinarians completed surveys based on chart reviews of 50 dogs (24 males, 26 females, mean age of 6.7 years). Sixty-three percent of follow-up examinations took place during the months from April to September. No follow-up was available for 2 dogs. The majority of dogs had been treated for at least 12 months with RESPIT at the time of the follow-up examinations (median 382, range 27 - 920 days). The 15 veterinarians who completed the survey were located in seven states (California, Florida, Illinois, Nevada, Oregon, Tennessee, and Texas). The allergen mixtures were different for each of these states.

The median pruritus severity and lesion severity were lower at the time of follow-up than on Day 1. Veterinarians assessed the overall efficacy as "good" or "excellent" in 69% of dogs evaluated beyond 90 days (29/42) and in 61% of all dogs treated (31/50). Adverse reactions (increased pruritus) were reported in 4/50 dogs resulting in the discontinuation of RESPIT in one dog.

The retrospective nature of this survey, the low participation rate and the likelihood of self-selection bias are significant limitations that affect the generalizability of these findings. It is, however, interesting that the response to RESPIT reported by 15 veterinarians for these 50 dogs is similar to the response rates often reported for allergen-specific immunotherapy in retrospective studies and for region-specific immunotherapy in the randomized-controlled trial by Garfield. Prospective studies are required to verify these findings.

Many thanks to those of you who participated in the study.