Pet Allergies Defined

Like people, allergies can affect dogs, cats and horses. However, allergies in pets usually appear as skin problems resulting in itching, scratching and chewing, which can lead to secondary infections. Pet allergies fall into three main categories including Flea Allergy Dermatitis (FAD), atopy and adverse reactions to food. Many pets can be affected by one or more of these allergies.

Flea Allergy Dermatitis
Flea Allergy Dermatitis (FAD) or “fleabite hypersensitivity” is a skin disease caused by an allergic reaction to flea saliva. A single fleabite can trigger the disease’s intense itching especially on the backs, legs, bellies or tails of pets. This often leads to “hot spots” or localized hair loss and skin infections.

A veterinarian diagnoses FAD by looking for unusual signs like scratching, skin sores and the presence of fleas or flea dirt. A veterinarian may also perform a skin test to confirm that fleas are the source of the problem since FAD symptoms can resemble other conditions, including external parasites (mites, lice), infections and other allergies that cause severe itching.

There is no cure for FAD because pets will always be allergic to fleabites. However, FAD can be prevented by using various insecticides and insect growth regulators that eliminate flea infestations, daily or routine vacuuming and frequent washing of a pet’s bedding to reduce a home’s flea population.

To break the “itch-scratch” cycle that leads to skin infections, a veterinarian may prescribe corticosteroids, antihistamines and essential fatty acids to relieve irritation. Warm-water baths and veterinarian-recommended anti-itching shampoos and conditioners may also help pets suffering from FAD.

Atopy is when a pet is genetically predisposed to be allergic, occurring when the pet has one or both parents with an allergic skin disease. An atopic pet will have an allergic reaction when exposed to substances like pollen, molds, house dust mites and other allergens. The incidence of atopy depends as much upon a pet’s genetic susceptibility as exposure to the allergen itself. Terriers, Setters, Retrievers, Dalmatians and Chinese Shar-Peis are particularly prone to atopy.

Atopy is associated with itching, mostly around the face, feet, lower chest and belly of pets. Depending on the cause, these symptoms may occur only seasonally (pollen) or year-round (molds, dust mites). “Hot spots” (pyoderma), other skin infections and ear problems can develop as well. Frequent scratching due to chronic irritation may lead to hair loss. These signs may be observed in pets from four months to seven years of age, but are typically noticed around one to three years of age.

Atopy is diagnosed through a process of elimination. Other causes of itching, such as fleas, mites, lice, bacterial yeast infections and food allergies must be ruled out first. A veterinarian will ask for a detailed history of the pet’s itching problem and may conduct skin or blood tests for different allergens to help pinpoint the exact cause.

Atopy is a lifelong condition with no known cure. However, there are a number of ways to manage the problem including anti-itch therapy with the use of drugs, medicated shampoos and conditioners, removal of the source of the allergy from the environment as much as possible and immunotherapy, which uses a series of injections to gradually accustom a pet’s system to the allergen(s) causing the problem. Although its effectiveness varies, this method provides at least some relief for around 75 percent of pets with atopy.

Adverse Reactions to Food (Food Allergy)
Adverse reactions to food occur when a pet has a dermatologically related reaction to one or more ingredients in its food. The most common allergens are beef and milk products, cereals (wheat, corn and soya), chicken and eggs. The exact cause of a food allergy is not known but could be associated with a change in the pet’s immune system causing certain ingredients to be perceived as “foreign,” initiating inflammatory mechanisms to fight off the perceived “intruder.”

The most common symptoms are itching, licking or chewing. Otitis Externa (ear infection) along with other skin problems are also common in conjunction with food hypersensitivity. Some pets may also have diarrhea and other digestive problems. Symptoms can appear at any age, whether a pet has just started a new diet or has been eating the same food for several years.

The only effective way for a veterinarian to diagnose a food allergy is for a pet owner to put their pet on a “hypoallergenic” or “exclusion” diet for a minimum of 8 to 12 weeks. This type of diet contains ingredients that the animal has not been exposed to in the past. Since the source of protein causes most allergic reactions, exclusion diets use proteins (often venison, fish or duck) that are not normally found in regular pet food. An exclusion diet may comprise of home-prepared food or prescription commercial hypoallergenic products.

If a pet has a food allergy, there should be a significant reduction in the symptoms after the recommended period on the exclusion diet. To identify all of the food allergens, a veterinarian will recommend adding a single protein back into the diet every one to two weeks, while watching for a recurrence or worsening of symptoms. If this happens the veterinarian will recommend removing the offending ingredient from the diet.

The most effective way to treat an adverse reaction to food in pets is to carefully monitor his or her diet in order to avoid flare-ups.



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