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Name
Food Allergy, Canine and Feline
Short Description
Food hypersensitivity
Affected Animals: Dogs, cats, and humans. Any age, sex, or breed of dog or cat can
develop food allergies.
Overview:
Ingredients in some pet foods may cause an
allergic reaction in hypersensitive cats and dogs. Reactions are
characterized by itching and gastrointestinal disorders, and are
usually responses to a protein or carbohydrate source in the diet.
Food allergies are the third most common cause of itching, and
account for about 10 to 15 percent of all allergic skin diseases in
canines.
Unlike animals with seasonal inhalant allergies, animals with food
allergies tend to itch year round, and do not experience much relief
from anti-itching medications. Therefore, it is essential to
identify and remove the type of food that is stimulating the
allergic response.
Some animals will have other allergies concurrently, such as
fleabite hypersensitivity and inhalant allergies, which have severe
symptoms when they are not controlled.
Clinical Signs: The only consistent sign of a food allergy is
pruritus, or intense itching, which typically continues throughout
the year and fails to respond well to corticosteroid treatments.
Various skin lesions may also occur, but there is no characteristic
pattern of lesions associated with food hypersensitivity. The ears,
axillae -- hollow areas under the front leg at the shoulder, groin,
and feet -- are affected more commonly than other body parts. Food
allergic dogs commonly present with ear infections in both ears. The
clinical signs of food allergies in cats are more variable than in
dogs. Cats may have miliary dermatitis, raised bumps with bloody
scabs, or eosinophilic granulomas, which look like elevated, open
sores on the skin. Vomiting, diarrhea, and more frequent but formed
bowel movements can be noted in some cases.
Symptoms:
See clinical signs.
Description:
A food allergy is an allergic reaction to a
substance within an animal's diet. Generally, the allergen is a
protein or carbohydrate source. Food allergy is strongly suspected
if the first signs of itching start before the dog is six months of
age or older than six years. Animals can have more than one type of
food allergy.
The exact mechanism of the disease is not completely understood.
Food allergies can affect the skin by causing itching and sometimes
skin lesions. The ears, feet, the hollow area under the front leg at
the shoulder, and groin are affected most commonly, although any
part of the skin can itch. The gastrointestinal tract may react to
the allergens as well; vomiting, diarrhea, and an increased number
of normal bowel movements per day are typical symptoms.
An elimination diet is fed exclusively to the animal in order to
diagnose definitively the food allergy. Food trials are performed to
determine the allergen or multiple allergens causing the animal's
reaction, so that the veterinarian can prescribe a tolerable diet.
Some animals may develop new allergies with time, but their diet can
be reformulated as necessary.
Diagnosis:
Before food allergy can be diagnosed, other
causes of itching and skin disease, such as flea bite
hypersensitivity and inhalant allergies, will need to be ruled out
as possible causes of the itching and gastrointestinal disorders.
The best tool for definitively diagnosing food allergy is a food
elimination diet, selected to contain a single protein and
carbohydrate source to which that the animal has not been previously
exposed. The special diet must be fed exclusively for a minimum of
13 weeks. If they have a food allergy, most animals will begin to
show signs of improvement within four weeks of the diet, but will
require feeding of the elimination diet for a longer time in order
to eliminate symptoms. Following the elimination diet, the original
food is fed to the animal to confirm that it does incite an allergic
reaction. If the animal is allergic to it, the return of clinical
signs will occur within 10 days of restarting the original diet.
Once the food allergy has been established, the exact allergen is
investigated by placing the animal on the elimination diet until it
is free of allergic symptoms. Subsequently, single food ingredients
are added to the elimination diet and the animal is assessed for an
allergic reaction. This process is repeated for each ingredient.
Commonly suspected allergens include beef, chicken, fish, pork, and
lamb meats; eggs and dairy products; and carbohydrate sources such
as corn, wheat, soybeans, rice, and potatoes.
Prognosis: The prognosis an animal with food allergy is good
if the allergens can be found and eliminated from the animal's diet.
Some animals will develop new food ingredient allergies with time,
and hence will need to have their feeding protocol adjusted as
necessary.
Transmission or Cause: The causes of food allergy are individual
allergens within the animal's food -- usually protein sources or
carbohydrates. It is suspected that certain preservatives or food
additives may elicit an allergic reaction.
Treatment: The allergen must be identified and removed from
the animal's diet. If present, secondary skin infections are
controlled using antibiotics or antifungal treatments. Concurrent
allergies must also be controlled. Anti-itching medications may be
used in the initial stages of treatment, but generally these drugs
are not effective for curing food allergy symptoms, and have to be
discontinued to allow correct assessment of food trials.
Prevention: Avoidance of allergens is the only known
preventative measure. No treats or other foods should be fed to an
animal with a food allergy. Because flavored medications such as
vitamins and heartworm prevention may cause an allergic reaction,
replacement with non-flavored pills is recommended.
