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When a dog or a cat has digestive upsets or other negative
reactions to a particular diet, food allergies are sometimes
thought to be the cause. The truth is food allergies
in pets are rare.
The vast majority of allergies in pets are due to
flee bites or contact with something in the environment.
Before making any judgement about food allergies, it
is important to understand what a food allergy is and
is not.
What is A Food Allergy?
Sometimes a food allergy is confused with food tolerance,
which results from the inability of the pet to digest
a particular food (such as lactose intolerance).
A food allergy is an abnormal immune response to an
individual food or additive. Signs of a food allergy
include itching and other skin problems or possibly
gastronomical disturbances such as diarrhea.
Food allergies can occur at any age. They develop over
time with repeated exposure to the same foods. Food
intolerance can occur the first time a food is fed.
Another aspect of a food allergy is its appearance
year-round. Other allergies (such as flea allergy dermatitis)
may be seasonal.
Changing Diets is Rarely Successful
Commercial pet food diets contain a large number of
ingredients and pets may be allergic to individual components
of the diet (lamb, chicken, beef, milk, wheat, corn,
etc.) rather that the diet itself. Food additives can
also trigger an allergic reaction in some pets. Every
component of the diet should be suspected. This is why
simply changing from one commercial diet to another
is seldom successful in controlling food allergies.
Many diets have the same ingredients and preservatives.
Elimination Diet Trial
Blood tests and intradermal skin tests may be useful
in identifying inhalant or topical allergies, but they
are unreliable in recognizing food allergy. Conducting
an elimination diet trial is the preferred diagnostic
method. The success of an elimination diet depends upon
identifying the food(s) responsible for the allergy
and eliminating them from the diet.
An elimination diet is restricted to those foods the
pet has previously not encountered. These foods are
described as hypoallergic because a pet cannot be allergic
to a food if it has never eaten it. There are no foods
that are completely nonallergic.
A special commercial diet, usually available from
a veterinarian may be tried. Or the owner, working with
a veterinarian, may prepare a homecooked ration.
Homemade hypoallergic diets are not nutritionally
complete and balanced and are not designed for long-term
use. A veterinarian should monitor the pet's health
and determine the length of the feeding trial.
During the food trial, only the homemade diet along
with fresh water should be fed. No food from the table,
chew toys, treats, flavored medicines (such as heartworm
preventatives or vitamin supplements) should be given.
The pet should be closely observed to be certain it
does not steal food from the table or from other household
pets or, in the case of some dogs, eat feces. Consumption
of any of these can invalidate a trial.
Trial Results
After a period of days to weeks the food-allergic pet
should show signs of improvement on the elimination
diet.
If a pet's condition does not improve during an elimination
trial, it is unlikely that the allergy is food-related.
Further diagnoses and tests are needed and the pet can
return to its original diet.
The final step in the diagnosis is to feed the pet
a meal consisting of its original diet. Most allergic
pets show signs within 72 hours of eating this diet.
Elimination diets are less effective if a food allergy
is only one component of a multiple problem, such as
concurrent flea or inhalant allergies. Pet's other allergy
problems may need to be addressed if the elimination
diet is to work properly.
If the elimination trial identifies an allergen, a
commercial diet that does not contain the offending
ingredient should be fed. The ingredients on pet snacks
should be carefully checked to be certain they are also
free of the allergen. The cooperation of all family
members is required if the food allergy is to be controlled.
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Reprinted with permission by Ralston Purina Canada
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