ALLERGEN-SPECIFIC immunotherapy is the mainstay of therapy for canine atopic dermatitis. But clients may be reluctant to administer the injections at home, and practitioners may find the process of finding the right dose and frequency to achieve an optimal effect frustrating. In this article, I review the efficacy of immunotherapy for treating atopic dermatitis, help you ease your clients' nerves about administering the injections, and show you how to easily adapt the administration protocol based on a patient's responses to the injections.
Allergen-specific immunotherapy's efficacy in dogs has been demonstrated in a blinded placebo-controlled study that revealed greater than 50% improvement in 59% of allergen-treated dogs and in only 21% of placebo-treated dogs.1 Numerous open studies have demonstrated similar results, with most showing that about 60% of dogs undergoing immunotherapy had good to excellent results. Some prospective studies have shown lower2,3 or higher4,5 (more than 90%) results in dogs that had their allergen-specific immunotherapy protocol altered based on patient response.
One prospective study evaluated allergen-specific immunotherapy in atopic dogs with house dust mite allergy that were treated with house dust mite allergen. This study was the first to monitor symptom, lesion, and medication scores as well as an owner global assessment.6 In 74% of the cases, the baseline symptom and medication scores were significantly reduced at the 12-month recheck, with 63% of cases having greater than 50% reduction. The owner global assessment was improved by more than 50% in 89% of the cases. When combined with other nonsteroidal treatments (antihistamines, fatty acids, and shampooing), allergen-specific immunotherapy was effective in more than 75% of the atopic dogs treated, and the dogs did not need systemic glucocorticoids.7
Allergen-specific immunotherapy is also the only treatment that has been described as curing atopic disease, though controlled studies supporting this statement are lacking.8,9
ADVANTAGES AND DISADVANTAGES
Effective allergen-specific immunotherapy may be more economical than many alternative options, especially in large-breed dogs. On average, a veterinarian pays about $7 for 1 ml of allergen, and most dogs will require 1 to 3 ml a month, with the average case requiring 2 ml of allergen a month. The only other cost is for the 1-ml syringes with needles. Since allergen-specific immunotherapy has not been associated with any organ disease or increased incidence of infections, this therapy does not require monitoring the results of complete blood counts, serum chemistry profiles, or urinalyses. Test costs should be factored in for therapies that require such monitoring. In addition, once maintenance therapy is reached, it is usually less labor-intensive than oral and topical treatments.
The disadvantages of allergen-specific immunotherapy include that it requires subcutaneous injections and that it is not a static therapy. Clinicians must learn how to make changes to optimize its efficacy. Failure to understand allergen-specific immunotherapy and how to modify it leads to frustration, and eventually clinicians abandon this effective and valuable treatment modality. There also may be a long lag time, with some dogs taking nine months to show a beneficial response.1 Published reports do not indicate responses faster than one month, but if glucocorticoids are avoided during the induction phase, it is not uncommon to see responses during the induction phase and the first month of therapy (Figure 1).
Figure 1. Client notes from a partial immunotherapy schedule and the client's assessment of pruritus, with 0 being no itch and 10 being severe itching. The owner assessment was a level 6 when allergen-specific immunotherapy was initiated, and by Day 5 the client assessed a decrease in pruritus by two levels and a greater than 50% reduction in pruritus by Day 9.