Allergies in Dogs

Summary

Canine allergies are common and occur when the immune system overreacts to allergens the dog is exposed to. The exact reason that the immune system overreacts is unknown, but is likely linked to breed or genetic predispositions. The most common canine allergens are flea saliva, grasses, dust mites, pollens, and meat proteins in the diet.

Dogs with allergies are very itchy, leading to excessive scratching, biting, or licking of itchy areas. There is no specific test to diagnose allergies. Other causes of itchiness, like parasites or skin infections, must be ruled out first. When necessary, skin tests and dietary trials are used to diagnose the specific allergens. Allergy treatment is individualized and complex, with options including avoidance (e.g. flea control), short-term glucocorticoids, maintenance allergy medications, limited-ingredient diets, and immunotherapy.  Allergies cannot be cured and require lifelong management.

Risk Factors

Allergies are very common in dogs. Although allergies are not life-threatening, the symptoms of allergies impact the dog’s quality of life and require prompt veterinary care. Without appropriate management of allergy symptoms, secondary bacterial fungal and skin and ear infections are common.

Diagnosis of allergies and identifying the best management strategy for the individual dog usually requires some trial and error. Working closely with a veterinarian is essential for a desirable outcome.

Possible Causes

Allergies occur when the immune system overreacts to allergens that it is exposed to. The reason some pets develop allergies while others do not is unknown. Some breeds are predisposed to allergies.

The most common allergens in dogs are:

• Flea saliva • Grasses • Dust mites • Pollen • Specific protein sources in food

Allergies are categorized several ways, and some dogs have multiple forms in response to the same allergen. The broad categories of canine allergies are:

• Contact allergies, including flea allergy dermatitis • Food allergies • Seasonal allergies

• Atopy (inhaled allergies)

Main Symptoms

Symptoms of allergies depend on the type of allergy response. In general, the main symptom of allergies is severe itch (pruritus). Signs of itchiness include:

• Excessive scratching • Biting or licking the area • Rubbing against surfaces • Rolling on the ground

• “Scooting” or dragging the rump on the ground

Other symptoms and conditions associated with allergies include:

• Watery eyes and runny nose • Digestive issues like vomiting and diarrhea • Ear infections

• Skin infections

Detailed Characterization

Allergic itch is more common at certain locations on the body:

• Lower back and base of the tail • Face, eyes, and chin • Ears • Front feet • Flanks

• Armpits 

Excessive scratching damages the skin, and often leads to other symptoms such as:

• Reddening, swelling, or crusting of the skin • Hair loss • Skin damage • Hives • Foul odor

• Scabs, crusts, and scales • Darkening and thickening of the skin • Greasy buildup

Testing and Diagnosis

Diagnosing allergies is complex, as there are many potential causes of itchiness. Multiple tests are run to rule out other conditions before coming to a diagnosis of allergies. These tests include: 

• Physical examination • Testing for bacterial, fungal, or parasitic infections • Bloodwork

• Biopsy of itchy or damaged areas to rule out tumors or other skin diseases

The type of symptoms, time when symptoms occur, and any trends in the symptoms helps categorize what type of allergy is occurring. Further tests to categorize the type of allergy include:

• Food elimination trials • Withdrawal testing • Patch testing • Intradermal allergy testing

Intradermal allergy testing can help identify what allergens the dog is allergic to. Allergy testing does not diagnose allergies. Results of these tests are only significant if they correspond with the dog’s type and timing of symptoms, and the dog’s symptoms resolve when the allergen is removed.

Steps to Recovery

Depending on the type of allergy and the specific allergens, the best strategy to resolve symptoms is to avoid exposure to the allergen. Avoidance strategies include: 

• Keeping the dog on effective flea control • Regular bathing to remove allergens from the dog’s skin

• Air filtration to remove allergens • Cleaning the dog’s environment • Limited-ingredient diets

Many cases of allergies benefit from medications that interrupt the “itch signal”, preventing the dog from experiencing itchiness. Severe symptoms may benefit from short-term use of glucocorticoids, but these are not appropriate for long-term use. Safer options for long-term management of allergy symptoms include both daily oral medications or an injection given as needed every few weeks.

Medicated shampoos and certain veterinarian-approved supplements are also helpful for helping to keep allergy symptoms at a tolerable level. The only treatment for allergies that approaches a cure is immunotherapy. A small amount of allergen is injected into the skin repeatedly over time until the immune system response to allergen is reduced. This is a complicated and lengthy process that is not always necessary for successful management of canine allergies.

Allergies are a lifelong condition. A combination of avoidance, ongoing management, and medications, is usually sufficient to keep an allergic dog comfortable and prevent secondary infections.

Prevention

The root cause of allergies is unknown so it is not possible to prevent them from developing. Symptoms can be successfully managed when exposure to the allergen is limited or eliminated.

Are Allergies Common in Dogs?

Allergies are very common in dogs. The most common type of allergy is flea allergy dermatitis, where dogs react to flea saliva. Other frequent types of allergies include:

• Atopic dermatitis • Environmental allergies • Seasonal allergies

Food allergies are very uncommon, affecting only 0.2% of dogs. Many dogs with food allergies have other types of allergies as well. Contact allergies are also very uncommon.

Typical Treatment

• Allergen avoidance • Environmental modification • Anti-itch medications • Allergen immunotherapy