Allergies are your pet’s immune system overreacting to something (allergen). The 3 most common allergies in pets are environmental, food and fleas. Most pets are on a flea & tick preventative, so this article is mostly about environmental and food allergies. In pets, allergic disease is typically expressed as itchiness.
ENVIRONMENTAL ALLERGIES
Atopy is the genetic tendency to develop allergic diseases. This is due to a heightened immune response to common substances in the environment, known as allergens.
In atopic dermatitis, also known as environmental allergies, the allergens make their way to the skin and then gain entry through a defective skin barrier. Inhaling is not necessarily involved. The most common allergies include:
- Pollens
- Dust particles/dust mites
- Molds
- Dander (skin cells, even from humans!)
- Grasses
The immune system becomes reactive to the airborne allergens, and then the itch is felt in the skin, leading your pet to experience licking, scratching, hair loss, redness, and skin thickening.
Meeting five criteria from this list yields an 85% accuracy for the diagnosis of atopic dermatitis, at least for dogs:
- Young Age of Onset- Seasonal itchiness due to atopy tends to begin early in a pet’s life (between ages 1 and 3 years in 70% of dogs diagnosed with atopy).
- Mostly indoor lifestyle- It is indoors where many airborne allergens are concentrated; however, it is important to note that allergens in the air are in the air for miles so it is not easy to escape allergens.
- Good response to steroids- Itchiness due to atopy responds rapidly to cortisone-type medications.
- Chronic or recurring yeast infections in the skin- Yeast & bacteria live on the surface of the skin normally but with all the changes allergy causes to the skin’s microenvironment, These microbes will proliferate and create a stinky, thickened, pigmented skin.
- Front feet involved- Foot licking and chewing on the tops/ in between toes is a classic sign.
- Ear flap involved- The inside portion of the ear flap is commonly involved in atopic dermatitis regardless of whether the inflammation extends down the ear canal and leads to what we usually think of as an ear infection
- Ear Margins NOT involved- Ear margin involvement is suggestive of sarcoptic mange and would lead one away from airborne allergies.
- Lower back area NOT involved- The lower back is the flea bite zone. There are few conditions other than flea bite allergy that cause itching in this area.
- Seasonality- Seasonality of the itching is also a clue towards an airborne-related allergy, but since there are many climates where seasons are ambiguous, this is not necessarily a hard and fast feature of atopic dermatitis.
FOOD ALLERGIES
Food allergies are another cause of itchiness for cats and dogs. Animals eat a variety of proteins and carbohydrates that are processed inside their bodies. Proteins may be combined or changed into substances recognized by the immune system as foreign invaders to be attacked. The resulting inflammation may target the GI tract or other organ systems; but in dogs and cats, the skin is frequently the target. Food allergies often require time to develop– most animals have been eating the offending food for years with no trouble.
The three most common food allergies are chicken, beef and wheat.
Clues that a pet has a food allergy:
- The itching is year round, not seasonal.
- Itching started when the pet was less than six months of age or greater than five to six years of age.
- No response to treatment for sarcoptic mange
- Corticosteroids have not been helpful in managing the itching. (Corticosteroids may or may not work on food allergy itching but they almost always work for other allergies.)
- There are accompanying intestinal signs like vomiting or diarrhea. These are seen in 30% of food allergic pets.
- The lesion distribution is compatible with food allergy, especially if an itchy anal area and/or recurrent ear infections are involved. (“Ears & Rear”).
To determine whether or not a food allergy is causing the skin problem, a strict diet trial is done. This means being fed a prescription diet, specifically made for pets with food allergies, for 8-10 weeks, with NOTHING else being given by mouth. These diets are specifically made for dogs with food allergies–over the counter diets will often have contaminants of other ingredients, which prescription diets for allergies do not.
FLEA ALLERGIES
Most flea-allergic pets lick, groom, and chew after being bitten by a flea. This causes the flea to either jump off the pet or be eaten by the pet. For this reason, most dogs and cats with severe flea allergies have never been found with fleas on them! In addition to causing severe itching, fleas can also cause other problems such as skin infections and hair loss. It is recommended to use flea & tick preventative year-round especially because of the inconsistent weather. Your pet should remain on monthly flea control year-round. Any pets in contact with that pet should also be on monthly flea control.
If there is evidence of flea bite allergy your pet’s veterinarian may ask you to treat your pet’s indoor environment for fleas with a spray designed to quickly kill fleas and stop their reproduction. To use a spray around your home:
- Remove your pets from the area to be sprayed.
- Wash all bedding.
- Vacuum all carpets and upholstery and then discard the vacuum bag (flea eggs can continue to hatch in vacuum bags).
- Spray all surfaces until damp to the touch.
