Allergen-Specific Immunotherapy: Hocus Pocus or Legitimate Therapy Holly Roberts, DVM, MS, DACVD 1. Allergic Disease a. Atopic Dermatitis i. Seasonal ii. Nonseasonal iii. Seasonally nonseasonal b. Cutaneous Adverse Food Reaction i. Nonseasonal c. Flea Allergy Dermatitis i. Typically, seasonal 2. Pathogenesis of Atopy a. Genetic predisposition i. Shift to Th2 response 1. Acute phase ii. Barrier defect 1. Filaggrin b. Sensitization i. Danger signals c. Re-Exposure i. Pruritus ii. Inflammation 3. Atopic dermatitis a. Clinical signs: i. Pruritus ii. Secondary lesions 1. Alopecia 2. Erythema 3. Excoriations 4. Hyperpigmentation iii. Recurrent infections 1. Pyoderma 2. Otitis b. Age of onset: i. Typically, 1-3 years c. Treatment i. Definitive therapy 1. Allergy testing with allergen specific immunotherapy (ASIT) ii. Symptomatic therapy 1. Glucocorticoids 2. Atopica 3. Antihistamines 4. Fatty acids
5. Cytopoint 6. Apoquel d. Intradermal Allergy Testing (IDAT) i. Pros 1. Testing target organ 2. Visibly witness mast cell degranulation 3. Type I hypersensitivity 4. More sensitive than serum testing 5. Cons ii. Requires sedation 1. Can be affected by endogenous steroid release 2. False positives 3. Medication withdrawals required e. Serum Allergy Testing (SAT) i. Pros 1. Only requires venipuncture 2. Can be on antihistamines ii. Cons 1. Measuring circulating immunoglobulins a. Non-skin specific 2. Variable labs a. Monoclonal vs. polyclonal antibodies 3. Medication withdrawals required f. Allergy Testing Withdrawals i. Steroids 1. Topical steroids a. >14 days (ideally 30 d) 2. Oral steroids a. >30 days 3. Injectable a. 8-12 weeks ii. Antihistamines 1. >14 days for IDAT iii. Fish oils 1. >14 days iv. Apoquel 1. Ideally 2 days, but can be tested on them v. Cytopoint 1. Can be tested on g. Saliva/Fur Testing i. Inaccuracy of hair and saliva testing for allergies in dogs ii. K. Coyner & A. Schick 1. Submitted samples for fur & saliva testing
a. 10 samples from known atopic dogs, non-allergic dogs, and fake fur from stuffed animals + tap water b. Positives in all categories c. Test results could not differentiate an allergic dog, nonallergic dog, or a stuffed animal 2. Not a recommended test h. Immunotherapy i. How it works 1. Allergen tolerance a. Desensitization 2. Alters antigen presenting cells 3. Th2 Th1/Treg response 4. Antibody isotype switching a. IgE to IgG4 ii. Allergen Specific Immunotherapy 1. Pros a. Patient specific b. Addressing underlying immune disease c. Minimal long-term side effects d. ~70% effective e. Sublingual or subcutaneous f. Prevents sensitization to other allergens??? 2. Cons a. 4-12 months to efficacy b. Moderate expense c. ~30% of failure 3. Subcutaneous immunotherapy (SCIT) a. Made specific for each patient b. Aqueous allergens i. Requires refrigeration c. 10-12 allergens per vaccine d. Less frequent i. Every 7-21 days ii. Concentration buildup over ~3 months e. Requires needle/syringe handling 4. Sublingual immunotherapy (SLIT) a. Made specific for each patient b. Glycerinated allergens c. 10-12 allergens per vaccine d. More frequent i. Once to twice daily ii. Concentration buildup over ~3 months e. Specialized bottle iii. Regionally Specific Immunotherapy (RESPIT)
1. Standard set of allergens in vx for each region 2. No allergy testing required 3. 18% improvement after a year a. ~70% improvement with ASIT 4. Exposure to new allergens may lead to further sensitization iv. Side Effects of Immunotherapy 1. Pruritus 2. Urticaria 3. Injection site reaction 4. Vomiting/diarrhea 5. Anaphylaxis v. Troubleshooting 1. Reaction during escalation phase a. Reduce concentration b. Decrease frequency c. Discontinue if reaction persists 2. Partial improvement after 1 yr a. Can add second vx 3. Increase/decrease frequency depending on response vi. Who should receive ASIT? 1. Patients who are a. Young to middle aged b. Non-responders to other therapies c. Have side effects with other therapies 2. Clients who a. Want to address underlying disease