Figure 3. Chronic otitis externa in a dog, a consequence of unmanaged food allergy.
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There is debate over the frequency of concurrent gastrointestinal signs in patients with dermatologic signs of adverse food
reaction.8,11 In my clinical experience, intermittent vomiting, diarrhea, colitis, or borborygmus occurs in 50% to 60% of dogs. Secondary
cutaneous or otic infections with bacteria or yeast also are common. It has been reported that adverse food reaction may respond
poorly to antipruritic doses of glucocorticoids, but most clinicians now agree this distinction is not a useful diagnostic
feature.
In cats
Cats often present with pruritus of the face and neck (Figures 4-6), although clinical signs can be diverse and include miliary dermatitis, symmetric alopecia, and manifestations of the eosinophilic
granuloma complex. Concurrent gastrointestinal signs have been reported in about 30% of cats.12-14 No age, sex, or breed predisposition has been noted in cats.
Figure 4. A 5-month-old cat at initial presentation with facial pruritus suspected to be due to food allergy.
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Figure 5. The same cat after 10 weeks on a limited-antigen diet. (Reprinted with permission from Foster AP, Foil CS. BSAVA
manual of small animal dermatology. 2nd ed. Oxford, UK: Blackwell Publishing, 2003.)
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PERFORMING A DIET TRIAL
Figure 6. A 4-year-old cat with severe facial pruritus and secondary infections. Subsequent evaluation showed this was caused
by adverse food reaction, and the cat was maintained long-term on a limited-antigen diet.
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The current gold standard method for identifying canine or feline adverse food reaction is to observe improvement of clinical
signs when the animal is fed a novel protein diet followed by a recurrence of clinical signs when a previously fed foodstuff
is reintroduced. This method generally requires feeding the novel diet for a minimum of six weeks, although some patients
may continue to improve for up to eight to 10 weeks, particularly if concurrent secondary infections are present.8
It is important to stress that canine and feline atopic dermatitis and adverse food reaction can present with identical clinical
signs and may in fact be concurrent problems. Consequently, I perform a limited-antigen food trial in all animals with nonseasonal
pruritus.
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