An allergy is a condition of unusual sensitivity to a
substance or substances usually protein in nature which
is perceived by the body as foreign. Signs of allergies
in dogs may manifest as itching and in some cases diarrhea.
Food allergies account for only about 5 to 10 percent
of all allergic reactions in dogs. Diagnosis of a food
allergy is a demanding diagnostic process requiring strict
dietary management to make sure no allergy-triggering
food is ingested by your dog.
Because the signs of food allergy resemble those of other
canine allergies - and because effective treatment depends
on pinpointing the allergy-causing ingredient - diagnosing
food allergies is challenging for both owners and veterinarians.
If your dog has an immediate adverse reaction to a diet
change, the reaction is probably not an allergy because
it takes more than one exposure to a food ingredient to
incite an allergic reaction. That’s why dogs that have
been eating the same food for months or years with no
problem can develop a food allergy.
The most common sign of food allergy is inflamed, itchy
skin, usually around a dog’s feet, face, ears, armpits,
and groin. The scratching and biting can lead to secondary
bacterial skin infections and ear canal infections.
Some food-allergic dogs experience vomiting and diarrhea
instead of - or along with - skin problems. Over the last
10 years in our practice, with the advent of endoscopy
( a fiber optic tube placed down into the stomach and
intestine of animals), we have diagnosed food allergy
as a component of vomiting and diarrhea. It is now felt,
that food allergy is the primary component in certain
cases of inflammatory bowel disease. By simply changing
the diet to a hypoallergenic diet , which we will discuss
later, and the intermittent use of corticosteroids, we
have successfully treated this disease.
If you bring your dog to the animal hospital with a complaint
of itching or digestive distress, your veterinarian will
first rule out more common causes of these signs. The
rule-out process might include a physical examination
and laboratory tests for flea allergy dermatitis, the
most common cause of allergic skin disease of dogs, inhalant
allergies, seasonal reactions to pollen, mold spores,
and dust mites, and food caused digestive intolerance,
an acute adverse reaction to food that does not involve
the immune system.
If the food allergy remains a suspect, your veterinarian
will then help you try to pinpoint what might be causing
your dog’s problems. Most food-allergic dogs are hypersensitive
to only one or two ingredients, with beef and dairy proteins
topping the culprit list. Ingredients that may also cause
problems - but not as often - include grains, pork, chicken,
eggs, and fish. Allergies to food additives including
preservatives may also be a cause but are rare.
To definitely diagnose food allergies, most veterinarians
recommend a trial with an elimination diet - a diet that
contains a protein and carbohydrate source the dog has
never been exposed to.
To start with, feed the elimination diet for a period
of up to 16 weeks and monitor your dog’s response. Signs
should abate if your dog is indeed food-allergic. Keep
in mind that it’s difficult to find elimination diets
in spite of the plethora of grocery- and pet-store offerings
because most such foods contain similar ingredients. Even
the so-called "hypoallergenic" lamb-and-rice
diets are unsuitable as elimination diets for many dogs
because they’re so popular the main ingredients are no
longer truly novel. Consequently, to carry out a valid
elimination-diet trial, you may have to either buy a therapeutic
diet from your veterinarian (which contains "exotic"
ingredients such as rabbit, venison, and potato) or some
of the newer "novel protein" diets that contain
a totally and nutritionally sound newly formulated protein
or prepare a home-cooked diet. Some of the manufacturers
are working diligently to develop these new hypoallergenic
diets.
Unfortunately in an attempt to capitalize on the use
of lamb as a health food, food manufacturers and retailers
sold a bill of goods to caring dog owners. It really is
no more nutritious than any other form of meat or poultry.
This particular product was used purely as an "elimination"
diet by veterinary dermatologists to diagnose food allergies.
As a result, we as a profession lost a readily available
source of food for allergy testing. Now we are using rabbits,
and venison (deer) as a source of hypoallergenic foods.
To get conclusive results from the trial, your dog should
ingest nothing but the elimination diet and water. That
means no treats, rawhide, or chewable medications. Following
this strict regimen can be difficult, especially for those
living in multidog households.
If signs are resolved after an elimination-diet trial,
you can assume something in your pet’s diet is causing
the allergy. But to be certain, some veterinarians recommend
reintroducing the original diet. A recurrence of signs
within 7 to 14 days confirms food allergy.
There is no cure for food allergies. Managing a food
allergy means simply avoiding the causative ingredient
or ingredients. Medications (such as antihistamines and
corticosteroids) that reduce itching caused by other types
of allergies usually don’t work on food-induced itching.
Long-term avoidance is simply a matter of keeping your
dog on the elimination diet you used to diagnose the allergy.
Unfortunately, however, some dogs become allergic to ingredients
in the elimination diet over time. If this happens to
your dog, you’ll need to find another nutritionally balanced
diet that contains "new" proteins and carbohydrates.
Although diagnosing and managing food allergies is challenging,
remember - most dogs are not food-allergic. So don’t automatically
think food if your pet has skin or digestive problems.
Whether you’re diagnosing a canine food allergy for the
first time or managing an ongoing case, you’ll need to
find an elimination diet that contains a protein and carbohydrate
source your dog has never eaten before. Often, the choice
boils down to either a commercial therapeutic diet from
your veterinarian or home-prepared food. Each has its
pros and cons.
Dry or canned commercial diets are convenient, nutritionally
balanced, and palatable. However, studies show that a
small percentage of food-allergic dogs react adversely
to commercial elimination diets that contain the some
basic ingredients as homemade diets that do not cause
a reaction. Experts surmise that manufacturing processes
may increase the allergenic properties of certain ingredients.
Two-ingredient homemade diets (such as chicken and rice)
are acceptable for the duration of a diagnostic food trial,
but they are not nutritionally complete. Concocting a
nutritionally balanced homemade diet for long-term feeding
requires the aid of a veterinary nutritionist, a lot of
time and expense, and the addition of nutritional supplements
that may themselves contain allergy-provoking proteins.
Thus, many veterinarians recommend starting with a commercial
elimination diet and resorting to a home-cooked approach
only if your dog doesn’t respond favorably to the commercial
food.
