Dog and Cat Allergies

By Nancy Otten, Animal Health Technologist

What are allergies and how do they affect our pets?

Allergies are an overreaction of the immune system.  The immune system reacts to a normally harmless substance as though it is something bad.  The most common way for these overreactions to be manifested is itchiness, either localized or generalized.  The respiratory system might also be affected.  Coughing, sneezing and runny eyes are often associated with these symptoms.  If your pet’s digestive tract is affected, you may see vomiting and diarrhea.

What are the most common types of allergies?

1. Flea allergies:

The most common type is flea allergy.  An animal that isn’t allergic to fleas suffers only a minor irritation when bitten.  When the animal is allergic to fleas (their saliva to be exact,) severe itchiness is produced.  They will scratch and scratch until often there isn’t any hair left and a big, open wound is produced.  The most common spot for this is over the rump, just before the base of the tail.  Presumably this is because the base of the tail is the flea’s favourite spot to bite.  However, these skin reactions can happen anywhere on the body.

2. Inhalent allergies

The next type is inhalant allergies.  Often these are seasonal allergies caused by things like ragweed and grass pollens.  Inhalant allergies can also be a year-round problem when your pet is allergic to things like dust mites or mold.   In people, these types of allergies cause sneezing, a runny nose and watery eyes.  In dogs and cats, however, the most common manifestation is generalized itchiness.   They will chew, lick and scratch almost any part of their body, including their face, ears and feet.  You’ll notice on dogs with light coloured coats that certain areas will turn a brownish orange.  That’s caused by excessive licking and saliva has stained the fur.

3. Food Allergies

The last type of allergy in dogs and cats is food allergies.   10-20% of allergic reactions in dogs and cats are food related.  They aren’t born with these allergies; it develops over time, anywhere from several months to several years.  Again, the body usually reacts with generalized itchiness, but they can also have respiratory symptoms and digestive problems.  2/3 of dog food allergies are beef, dairy or wheat.  90% of cat food allergies are beef, dairy or fish.

How do I know if my pet has allergies?

Your first course of action would be to see a veterinarian.  I wouldn’t encourage diagnosing this on your own because these symptoms are common with other diseases as well.  If the vet determines that allergies are the most probable cause, you can do allergy testing.  Skin testing is probably the best way to do this.  They would inject small quantities of the most common allergens into the animal and observe skin reactions. These tests do have limitations though.

How do we treat allergies in dogs and cats?

If it’s a food allergy, you need to switch your pet to an elimination diet.  You need to feed them a diet with protein and carbohydrate sources that your pet has never been exposed to before.  This sounds easier than it really is.  It has become harder and harder to find novel food sources.  Lamb and rice used to be uncommon food sources so we could use them in an elimination diet.  Now lamb is in so many different pet foods that we have lost it as a form of unique protein.  Venison, rabbit and potato are ingredients in the newer elimination diets.  Also, through research they’ve discovered that the allergies are caused by very large protein molecules.  They’ve now made diets where these large molecules are broken down thus eliminating the allergen.  Rarely, your pet can be allergic to the preservatives in food.  If this is the case, you may have to go to a homemade diet.  This must be done with the guidance of a veterinary nutritionist because it is really easy to cause nutrient deficiencies this way.  You should know that it can take up to 12 weeks, or more, of feeding the new diet before any improvement is seen.  This is a real test of patience and determination.  It also means no more treats for the pet, which is really hard to do especially when out and about.  You need to make sure that your dog doesn’t find any food lying around or that any good-hearted, but misguided, individuals don’t slip your pet a bit of their burger.

Inhalant allergies are hard to treat because it is often very difficult to avoid the things that are causing the problem.  If it is seasonal allergies, treatment is a bit easier.  If your pet’s allergy symptoms are only around for a short time every year, steroids might be the answer.  Steroids will block the allergic reaction.  Long-term steroid use isn’t optimal though.  Antihistamines are sometimes affective but use them under the guidance of your veterinarian so that you get the dosage right.  A drawback to antihistamines is sedation, which happens to people too.  You may have to try several brands before you find one that doesn’t make your pet sleepy.  It has been shown that frequently bathing your pet with a hypoallergenic shampoo is helpful.  It soothes the inflamed skin and also washes away any allergens that have deposited on the coat.

Flea allergies are solved by controlling the flea population on your pet and in your home.  If you have an infestation you’ll need to treat your premises as well as your pet.  Since it’s the flea bites that cause the problem, you will need to use an adulticide, like Advantage, which means that the adults will die before they bite your pet.  As a precautionary measure it is also recommended that you use a product like Program simultaneously.  These types of products act as birth control so that if, by chance, a flea does bite your pet and lays eggs, those eggs will never hatch. 

People can get allergy shots.  Are these available for pets?

Yes, this type of therapy is available but it is very expensive, and it can take up to a year to work.  Anywhere from 50-70% of the animals that undergo it have adequate relief from their symptoms.  The use of steroids interferes with this process so if steroids are the only form of relief for your pet, you wouldn’t be able to do it.