Food hypersensitivity in dogs
No age or sex predisposition is known to exist regarding the development of food allergy in dogs, but as many as 50 percent
of patients with food allergies may exhibit clinical signs at less than 1 year of age. The so-called allergic breeds such
as Cocker spaniels, Springer spaniels, Labrador retrievers, miniature schnauzers, Shar Peis, West Highland white terriers,
Wheaten terriers, German shepherds and Golden retrievers may have a higher rate of food allergy. I have seen a higher rate
of food allergy in three dog breeds—German shepherds, Rhodesian ridgebacks and Shar Peis.
Clinical signs vary, but nonseasonal pruritus, otitis and dermatitis are frequently seen. Sometimes the clinical signs are
as simple (or vague) as recurring pyoderma or a nondescript keratinization disorder (seborrhea). Food allergy should always
be considered in any patient with recurring urticaria, and eosinophilic vasculitis has also been associated with ARF.
In general, the clinical signs of food allergy are nonseasonal, although they could be episodic if they are due to sporadic
treat administration. It is also possible for the effects of a food allergy to be low or subclinical (below a pruritic threshold)
and only occur with the addition of environmental allergens will the patient flare.
Any dog with a nonseasonal pruritic dermatosis should have food allergy ruled out as a contributing cause of the skin disease.
Several other clues may raise your index of suspicion that a patient is suffering from a food allergy. One is the pattern
of skin disease. Food allergies are known to commonly affect the "ears and rears" of the patient. Another potentially useful
clue is the response to corticosteroids. Atopic dermatitis is usually responsive to corticosteroids at anti-inflammatory doses.
While some patients with a food allergy will be very responsive to corticosteroids, some will not, and when the pruritus is
not corticosteroid-responsive, food allergy should be considered.
Nearly half my patients have gastrointestinal manifestations of their ARF. Dramatic gastrointestinal signs include vomiting
and diarrhea, but they may be as subtle as flatulence or frequent (more than twice a day) bowel movements.2 Rarely reported clinical signs of ARF include seizures and respiratory signs such as bronchitis, rhinitis and chronic obstructive
pulmonary disease,3 all of which I have seen.
Feline food allergy
No age or sex predisposition has been reported or recognized in cats with food allergies. One study in cats with food allergies
reported the offending allergen had been fed for more than two years on average.4 Siamese and Siamese crosses may be predisposed to food hypersensitivity. The classic or hallmark clinical sign of food allergy
in cats is pruritus, especially of the head. Cats may also exhibit self-induced alopecia or any manifestation of the eosinophilic
Definite diagnosis of an ARF requies an elimination diet trial. Part 2 of this two-part series will cover how to conduct a
successful trial and help patients get rid of the itch once and for all.
Dr. Lewis sees dermatology patients in California, Azrizona, Nebraska, New Mexico and Washington. In 1991, he established Dermatology
for Animals, PC.
1. Jeffers JG, Meyer EK, Sosis EJ. Responses of dogs with food allergies to single-ingredient dietary provocation. J Am Vet Med Assoc 1996;209(3):608-611.
2. Paterson S. Food hypersensitivity in 20 dogs with skin and gastrointestinal signs. J Small Anim Pract 1995;36(12):529-534.
3. White SD. Food allergy in dogs. Compend Contin Educ Pract Vet 1998;20:261-268.
4. White SD, Sequoia D. Food hypersensitivity in cats: 14 cases (1982-1987). J Am Vet Med Assoc 1989;194(5):692-695.