Sunday, March 30, 2014

Understanding Dog and Cat Allergies

www.providencevet.comAllergies in dogs and cats can be very confusing and extremely convoluted. I will attempt to simplify the allergy subject into simple concepts and categories. Since spring is about to come on the scene, allergies always become more obvious in dogs and cats at this time. Allergies can always be present, but spring seems to heighten the clinical signs and therefore your awareness.

Just as allergies are increasing among humans, veterinarians are also seeing significant increases in allergies in dogs and cats.  Interestingly, the symptoms of canine and feline allergies cause different symptoms than typical “hay fever”—known clinically as allergic rhinitis in people. While people sneeze and wheeze, dogs and some cats tend to itch and scratch or have gastrointestinal signs!  

Some common signs of allergies in dogs and cats are:
  • Seasonal or non-seasonal itching, licking, scratching, rubbing
  • Foot licking, face rubbing/scratching
  • Rashes or patchy areas of redness
  • Recurrent ear infections or head shaking
  • Recurrent skin infections
  • Patchy hair loss
  • Respiratory distress
  • Loose bowels
OK, so what are allergies? Just like people, dogs and cats can show allergic symptoms when their immune systems begin to recognize certain everyday substances—or allergens— as dangerous to their bodies. Even though these allergens are common in most environments and harmless to most animals, a dog with allergies will have an extreme reaction to them. Allergens can be problematic when inhaled, ingested or contact a dog’s skin. As his body tries to rid itself of these substances, a variety of skin, digestive and respiratory symptoms often appear.

Allergies have been divided in articles into 3, 4 ,5, and 6 subjects or more. This tends to confuse the most organized person. For our purposes, we will divide allergies into two main groups:

Food Allergies
Environmental allergies

Food Allergies can be tested by using the pet's blood. Usually 25 or 30 ingredients are tested this way. It is about 80 - 85% accurate. The treatment answer is to avoid the foods that are shown to be reactive on testing. In my hands, this has worked quite well and is very convenient to the owner.

The alternative is through a strict “hypoallergenic” dietary trial for 8-12 weeks. Protein sources are the most common food allergens. Therefore, novel protein diets are most often recommended as they contain unique protein sources (rabbit, venison, duck based diets) to which your pet has not been exposed to in the past. Prescription diets are preferred because these diets are highly purified and not contaminated with other protein sources (such as beef or chicken) which can occur under less strict manufacturing processes. Once food allergens are identified, control is through strict avoidance of these ingredients as well.

Environmental allergies are every antigen known on earth, inside or outside your home. Let's try to break this down. Inside your home would include such items as dust mites, molds, fungus, bacteria, and various aerosols found in the home.

Outside your home would include trees, shrubs, weeds, grasses, pollen, insects, mites, fungus, and some molds.

These are the same allergens that cause “hay fever” in people.  When concentrations of these airborne allergens increase, it can trigger itching and secondary ear and skin infections in some dogs. This condition is known as atopic dermatitis . Certain breeds appear more likely to developing these types of allergies.
Symptoms can be seasonal or non-seasonal depending on what specific allergens are bothering your dog or cat. Facial rubbing and foot licking are the most common types of itching seen; repeated ear and skin infection are common.  Diagnosis is made based on the pattern of itching and eliminating all other causes of itching (bacteria and yeast infections, food allergy, flea allergy and other parasitic infections such as lice and mites).

Unfortunately, there is no cure for environmental allergies and therapy for this disease is life-long. However, symptoms are highly manageable. Milder cases are often controlled with antihistamines and topical therapy alone. In more severe cases, your veterinarian or veterinary dermatologist may recommend allergy testing (skin or blood testing) which can be used to identify specific allergens to which your pet is reacting. I prefer the blood test. It is convenient, easy for the pet in terms of stress and time. When the results are in, allergy injections given over time can then help reduce your pet’s sensitivity to these allergens.  Because this therapy can require 6-12 months for benefits it is often combined with other anti-itch therapies (drugs, topical shampoos, rinses and sprays) to help keep your pet comfortable.  

Dividing allergies into two categories is helpful. Just keep in mind, when you see
  • Those caused by fleas and other biting insects (flea allergy dermatitis)
  • Those caused by inhaled allergens such as dust mites, grasses, molds, and tree and weed pollens (canine atopy)
  • Those caused and by foods and drugs (food allergies)
  • Those caused by irritants that have direct contact with the skin (contact allergies) 

We are still talking about the same process.

  • Allergies caused by airborne particles are called atopy. Common sources are pollens, molds, and dust mites.
  • Allergies that result from flea-bites are referred to as flea allergy dermatitis.
  • Certain allergies occur from items your pet ingests, and are typically called food allergies.
  • Contact allergies are caused by something your pet comes in direct contact with, such as carpet fibers, plastics, and other things. Contact allergies are far less common than atopy and flea allergy dermatitis in pets.

We are still talking about the same process.

Remember, treatment is avoidance of foods that are known to react in your dog or cat. For the environmental antigens, there is immediate symptomatic treatment, which is temporary (days or weeks) and desensitization injections, which take 6 - 12 months to actually help, but are life lasting if you continue the treatment.

The Providence Veterinary Hospital Blog is a publication of Peter Herman, VMD, at the Providence Veterinary Hospital, 2400 Providence Ave. in Chester, PA. Contact Dr. Herman at 610-872-4000 or visit us at