Pets with concurrent allergies
As previously discussed, the incidence of concurrent atopic dermatitis and adverse food reaction is unknown in dogs and cats.
However, some patients will have a history of year-round pruritus that worsens in the spring and summer. In these cases, it
is important to consider the possibility of concurrent adverse food reaction, atopic dermatitis, or flea allergy dermatitis.
Depending on the time of year the diet trial is initiated, these patients may not exhibit complete resolution of pruritus,
but they should show some improvement with dietary restriction and relapse of pruritus on dietary challenge. Many dermatologists
prefer to perform diet trials and challenge during the winter to avoid seasonal increases in pruritus due to environmental
allergens, complicating interpretation of the diet trial.
ALTERNATIVE IDENTIFYING TESTS FOR FOOD ALLERGY
Unfortunately, no other reliable tests for identifying food allergies in pets are currently available. Various authors have
looked at intradermal testing with food allergens and measurement of food-specific serum IgE. Although dogs with atopic dermatitis
are more likely to have positive intradermal test reactivity to foodstuffs than are normal dogs,21 this test is unreliable for identifying food hypersensitivities.7,16 In addition, food-specific serum IgE measurement has not proved to have a useful degree of sensitivity for clinical diagnosis
in its current form.7,16 Although these tests are commercially available, I do not recommend their use for diagnosing adverse food reaction in dogs
NUTRITIONAL MANAGEMENT OF PATIENTS WITH ADVERSE FOOD REACTIONS
Most patients can be managed long-term with a commercial limited-antigen or hydrolysate diet, and many owners elect to continue
feeding the trial diet. Home-cooked diets must be balanced for long-term feeding. However, if specific allergens have been
identified, it may be possible to extend the choice to diets readily available over the counter. An unanswered question is
how often pets develop an allergy to the new diet. This is recognized in dermatologic practice and should be considered in
patients that relapse. Typically, changing to an alternative diet with different protein and carbohydrate sources will resolve
the clinical signs.
Clinical evidence suggests that adverse food reactions occur quite commonly in dogs and cats, and further research with animal
models will help elucidate the pathogenesis. Nonetheless, in all animals with a nonseasonal pruritus, consider adverse reaction
alone or concurrent with environmental hypersensitivities. With good client education, a valid diet trial confirmed with provocative
challenge is a realistic undertaking. Dietary management offers a good long-term prognosis for affected dogs and cats.
Hilary A. Jackson, BVM&S, DVD, DACVD
Dermatology Referral Services
528 Paisley Road West
Glasgow G51 1RN, Scotland
1. Leung DYM, Bieber T. Atopic dermatitis. Lancet 2003;361:151-160.
2. Jackson HA, Murphy KM, Tater KC, et al. The pattern of allergen hypersensitivity (dietary or environmental) of dogs with
non-seasonal atopic dermatitis cannot be differentiated on the basis of historical or clinical information: a prospective
evaluation 2003-2004. Vet Dermatol 2005;16:200.
3. de Weck AL, Mayer P, Stumper B, et al. Dog allergy, a model for allergy genetics. Int Arch Allergy Immunol 1997;113:55-57.
4. Ermel RW, Kock M, Griffey SM, et al. The atopic dog: a model for food allergy. Lab Anim Sci 1997;47:40-49.
5. Olson M, Hardin JA, Buret A, et al. Hypersensitivity reactions to dietary antigens in atopic dogs. In: Rheinhart GA, Carey
DP, eds. Recent advances in canine and feline nutrition, Vol. 3. Wilmington, Ohio: Orange Frazer Press, 2000;69-77.
6. Jackson HA, Hammerberg B. Evaluation of a spontaneous canine model of immunoglobulin E-mediated food hypersensitivity: dynamic
changes in serum and fecal allergen-specific immunoglobulin E values relative to dietary change. Comp Med 2002;52:316-321.