Canine allergic dermatitis: Pathogenesis, clinical signs, and diagnosis - Veterinary Medicine
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Canine allergic dermatitis: Pathogenesis, clinical signs, and diagnosis


Clinical Edge


Much has been written about the pros and cons of intradermal vs. serum IgE testing, and this is well reviewed in many sources.1,7,11,12 Briefly, intradermal testing measures the skin's reactivity to allergens injected intradermally, and serum IgE tests measure the reactivity of IgE antibodies in the blood to a particular allergen. Both tests can be used successfully to prepare immunotherapy formulations. The advantages of serum IgE testing include convenience of a single blood draw, less patient stress, no haircoat clipping, less likelihood of a false negative test result due to drugs or sympathetic nervous system response hormones, widespread availability, and lower cost. Seasonality has not been thought to affect the test; however, this has not been my experience. It is well established that only partial correlation exists between serologic and intradermal testing, and the relevance of this is unknown.11 It is important to remember that normal dogs can have positive intradermal and serum IgE test results.

My practice encompasses both referral patients and primary first opinion patients. After reaching a clinical diagnosis of atopic dermatitis, the decision as to which test to use (intradermal vs. serum IgE) depends on the individual patient and the client's resources and preferences. In most cases in which the patient has not had previous diagnostic testing for allergies, I recommend serum IgE testing. If the patient has had previous serum IgE testing and immunotherapy has failed based on that testing, my recommendation is to consider intradermal testing. In some cases, both tests are performed to identify important allergens.

References

1. Scott DW, Miller JH, Griffin CE. Hypersensitivity disorders. In: Muller GH, Kirk RW, eds. Small animal dermatology. 6th ed. Philadelphia, Pa: WB Saunders Co, 2001:571-650.

2. Medleau L, Hnilica KA. Hypersensitivity disorders. In: Small animal dermatology: A color atlas and therapeutic guide. 2nd ed. St. Louis, Mo: Elsevier, 2006;159-188.

3. Marsella R. Contact hypersensitivity. In: Campbell KL, ed. Small animal dermatology secrets. Philadelphia, Pa: Hanley & Belfus, 2003;202-208.

4. Morales CA, Schultz KT, DeBoer DJ. Antistaphylococcal antibodies in dogs with recurrent staphylococcal pyoderma. Vet Immunol Immunopathol 1994;42:137-147.

5. Farver K, Morris DO, Shofer F, et al. Humoral measurement of type-1 hypersensitivity reactions to a commercial Malassezia allergen. Vet Dermatol 2005;16:261-268.

6. Moriello KA. Feline atopy in three littermates. Vet Dermatol 2001;12:177-181.

7. Mueller RS, Jackson H. Atopy and adverse food reactions. In: Foster A, Foil CS, eds. BSAVA Manual of Small Animal Dermatology. 2nd ed. Woodrow House, Gloucester UK: BSAVA, 2002;125-136.

8. Marsella R. Atopy: New targets and new therapies. Vet Clin North Am Small Anim Pract 2006;36:161-174.

9. Olivry T, DeBoer DJ, Griffin CE, et al. The ACVD task force on canine atopic dermatits. Vet Immunol and Immunopathol 2001;81:143-383. (Note: This entire volume is devoted to an in-depth critical literature review on all aspects of canine atopy.)

10. Willemse T. Atopic skin disease: a review and reconsideration of diagnostic criteria. J Small Anim Pract 1986;27:771-778.

11. DeBoer DJ, Hillier A. The ACVD task force on canine atopic dermatitis (XVI): Laboratory evaluation of dogs with atopic dermatitis with serum-based "allergy" tests. Vet Immunol and Immunopathol 2001;81:277-287.

12. Hillier A, DeBoer DJ. The ACVD task force on canine atopic dermatitis (XVII): Intradermal testing. Vet Immunol and Immunopathol 2001;81:289-304.


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