Atopic Dermatitis (Inhalant Allergies) in Dogs

Summary

Atopic dermatitis (or atopy) is a common allergic condition in dogs that is similar to human environmental allergies (hayfever). Determining what the dog is allergic to is rarely necessary for management of the disease, but examples of common dog allergens include pollen, dust mites, and mold spores. 

The primary symptom of atopy is itching (pruritus), particularly of the feet, face, ears, armpits, abdomen, and inner surfaces of the legs.  As the condition intensifies, the skin becomes more inflamed and scratching may lead to skin damage and hair loss. Secondary bacterial and fungal ear and skin infections are also common in dogs with atopic dermatitis. 

The diagnosis of atopic dermatitis is challenging. There is no specific test for atopy, and there are many potential causes of itching in dogs. Veterinarians sometimes use diagnostic tools like intradermal skin testing or blood testing to narrow down the cause of itching, but the diagnosis of atopy is based on the dog’s history and clinical signs after ruling out other conditions associated with pruritus. 

Treatment of atopic dermatitis is very complex. Allergies are chronic and life-long, so treatment protocols focus on managing the allergy rather than curing it. Medications are used to relieve the itch, and environmental measures are also helpful in reducing exposure to allergens.

There is no cure for atopy, but allergen immunotherapy can significantly reduce symptoms. Immunotherapy is similar to human allergy shots, where small amounts of antigen (the protein identified as causing the allergic reaction) are injected into the dog’s skin on an ongoing basis. 

Over time, these injections can reduce the immune system’s response to the allergen. These treatments can take up to a year to show results, and up to 25% of dogs have no changes in their symptoms despite this treatment.

Risk Factors

Atopic dermatitis is very common in dogs, with 3-27% of dogs affected. Atopy is not life-threatening, but the symptoms of allergies continue to worsen without appropriate treatment, impacting quality of life for the dog and humans in the household. 

Dogs that are constantly itchy or have developed hair loss, reddening of the skin or skin damage require veterinary attention as soon as possible.

Diagnosis and treatment of atopic dermatitis can take a significant amount of time and a lot of trial and error. Working closely with a veterinary team is crucial for a successful outcome.

Possible Causes

In general, the causes of allergies are unknown. Genetic predisposition has been identified and environmental factors likely play a role, but a root cause has not been identified conclusively. 

Atopic dermatitis occurs when the immune system overreacts to something in the environment. When the dog inhales the allergen, an inflammatory response begins, triggering itching in the skin. The main inhalant allergens in dogs are:

• Pollens • Dust mites • Mold spores • Animal or human dander • Insects • Environmental yeasts

Main Symptoms

The major symptom of atopic dermatitis is severe itching, often of the feet, face, ears, armpits, abdomen, and Inner surfaces of the legs. Dogs generally first develop symptoms between 6 months and 3 years of age.

Detailed Characterization

Severe itching can lead to skin damage and potentially infection. Secondary symptoms include:

• Reddening of the skin • Patches of gray skin (hyperpigmentation) • Hair loss • Crusting of the skin

• Scratches or scrapes • Thickening and hardening of the skin • Ear infections • Skin infections

The severity of symptoms can vary with changing seasons or exposure to different environments, due to the different allergens inhaled by the dog.

Testing and Diagnosis

Diagnosis of atopic dermatitis can be challenging. Other potential causes of itchiness must be ruled out before a diagnosis can be made, because there are no specific tests for atopy. Conditions that must be ruled out include:

• External parasites like fleas or mites • Skin infections • Food allergies • Flea allergy dermatitis

• Skin irritation • Skin tumors

To rule out these conditions, veterinarians use some or all of the following tests:

• Skin scraping: Where the skin is scraped and any cells or parasites collected are examined under a microscope.

• Fungal culture, skin and ear cytology, skin and ear swabbing: to identify the presence of yeast and/or bacterial infection.

• Flea combing and hair plucking: to identify external parasites.

• Skin biopsy: A sample of skin is submitted to a pathologist to identify disease or infection. 

• Bloodwork: to rule out other diseases and inform general health status.

• Dietary trials: Dogs are placed on a diet with no known allergens, to see if their allergies are food-related. 

Allergy testing can help identify what the dog is allergic to. It is important to note that allergy testing does not diagnose allergies. Allergy test results are only considered significant if they correlate with the dog’s symptoms in terms of seasonality, history of exposure, or reduced symptoms when the allergen is removed.

Steps to Recovery

Atopic dermatitis is a life-long condition. With appropriate management, the severity of symptoms can be reduced. A combined approach of medication and environmental management can help reduce symptoms. Immunotherapy injections may also help reduce symptoms in the long term in the majority, but not all, cases of canine allergies.

A combination of steroids and anti-itch medication may be recommended to manage symptoms. Many dogs also have secondary bacterial and/or fungal infections that require appropriate antimicrobial therapy, either orally or in medicated shampoos. 

Maintaining best skin care practices as recommended by a vet also helps to reduce the itching caused by atopy. This includes staying current with external parasite control and regular bathing.

Managing allergen levels in the environment is an important aspect of treatment. Strategies include:

• Regular, thorough cleaning of the household

• Washing bedding and stuffed toys regularly

• Minimizing the number of house plants

• Air filtration systems

Prevention

Allergies can not be prevented, only managed. They are not contagious, but genetic predisposition to atopic dermatitis has been identified. Symptoms can be reduced using a combination of medication, skin care practices, and environmental management.

Is Atopic Dermatitis Common in Dogs?

Atopy is very common in dogs. Studies have shown 3-27% of the dog population have atopic dermatitis.

Typical Treatment

Treatment depends on the individual case and how the dog responds to different strategies. In general, treatment will include medication to control itching, medication to treat secondary infections, environmental controls, and adherence to robust skin care routines. Immunotherapy may be recommended and help reduce symptoms in the long term.