The changing leaves are a universal signal that autumn has arrived. In the animal hospital, another sure sign of the season is the increase in allergy calls. Like people, dogs and cats can develop allergies to many things, including food, dust, mould, and pollen.
What are Allergies?
An allergy is an overzealous immune response to everyday environmental and dietary factors. When an allergic individual is exposed to these factors, called allergens, they experience an inflammatory reaction that can be uncomfortable and even dangerous. Allergies are often categorized source: food allergies, indoor and outdoor environmental allergies, and flea allergies are some common examples. Pets can be exposed to allergens through skin contact, inhalation, or ingestion. Like people, pets often react to more than one allergen in their environment and/or diet. Fall is a prime time for outdoor allergens.
Signs of Seasonal Allergies in Dogs and Cats
The most common sign of seasonal allergies in dogs and cats is itchy, inflamed skin. Allergic dogs will scratch, lick and chew more at their ears, armpits, bellies, and feet, and they may scoot on their behinds. Cats tend to rub and scratch their heads, necks, ears, and chins, and they may develop inflammatory plaques and sores. Sneezing, wheezing and runny eyes or noses are some of the less common signs of allergies in pets. Pets with allergies experience more skin, ear, and eye infections and are more likely to need to visit the vet for prescription medication.
Pets with year-round itchiness often have allergies to food or indoor allergens such as dust, wool, and indoor moulds. Pets with a clear seasonal pattern to their itchiness are more likely to react to outdoor allergens like pollen, grass, and outdoor moulds. Signs of flea allergies come and go with flea exposure, but flea populations also peak in the fall.
Diagnosis of Seasonal Allergies
There is no specific test that can demonstrate that a pet has allergies. Instead, a diagnosis is made based on the pet's history, clinical signs, physical examination findings, and by ruling out other causes of itchiness such as parasite infestation, endocrine disease, and cancer. Pet owners may be asked to complete a survey about their pet's lifestyle, diet, and environmental exposures. A pet that shows signs of allergies will be treated with a flea control medication. The veterinarian will examine skin and hair samples under the microscope to check for parasites, bacteria, and yeast. Blood tests should be performed to evaluate organ function and thyroid health. Occasionally, skin biopsies may be examined. When all other causes of itchiness are ruled-out, a diagnosis of allergies can be made. Once the allergic disease has been confirmed, blood and skin allergy tests can be used to identify the precise allergens responsible for the pet's discomfort. Allergen identification is used to design the treatment approach.
Currently, 10-15% of dogs and cats suffer from environmental allergies (1,2). The tendency of allergic disease to run in families demonstrates that allergies can be inherited (1). Genetic analysis shows that the genes responsible for immune system function are expressed differently in allergic dogs than normal dogs (1). Affected dogs are more likely to respond to allergens with a strong inflammatory reaction. In addition to this, allergic dogs have less protective skin barriers, allowing more allergen contact, and leaving the pets more susceptible to secondary infections (1). The underlying causes of allergies are not as well understood in cats, but a genetic predisposition is also suspected (1).
Allergy Treatment Options
Good vet-client communication is the most critical tool for treating allergic diseases in pets and managing clients' expectations. Allergies are a chronic condition in pets; they cannot be cured, and they require ongoing efforts from pet owners and their veterinarians. Pet owners need to know this upon diagnosis to prevent frustration when a cure is unavailable.
Whenever possible, avoiding an allergen is the most effective management approach with the lowest side effects. Many dogs and cats react to more than one allergen. The combined exposures to parasites, food and environmental allergens contribute to the itchiness and skin disease that a pet will experience. The first steps in allergy treatment always include flea prevention and the introduction of a hypoallergenic diet. Indoor allergens can be reduced by providing clean, wool-free, dust-free bedding and confining pets to non-carpeted areas of the home. Outdoor allergens can be more challenging to avoid. If the precise allergen is known, walking routes and environmental pollen reports can be used to minimize exposure.
Itchiness, scratching, chewing and overgrooming are distressing to both the pet and the owner. Providing comfort and reducing itchiness is a vital part of treating allergies. Corticosteroids, immune-suppressing drugs, and immune-modulating drugs can all be used to reduce inflammation and itch in pets. These drugs address the symptoms of allergic disease, but not the cause. Some medications, such as corticosteroids, are associated with side-effects that make them less suitable for long-term use. Other drugs, such as cyclosporine and lokivetmab, show better long-term safety but can be cost-prohibitive, particularly in larger patients (4). For these reasons, therapeutic approaches that address the cause, such as avoidance and immunotherapy (see below), remain essential.
Treatment of Secondary Infection
Due to allergies, inflammation of the skin creates a warm, moist environment that is perfect for bacteria and yeast growth. Scratching and over-grooming disrupt the skin's protective barrier and allows infections to flourish. When allergies are treated, these secondary infections also need to be treated, and the skin barriers restored. Antibiotics and antifungal medications can be delivered by mouth, by injection, or topically to control infection. Supplements and topical products containing essential fatty acids, ceramides and lipids help reduce inflammation and improve the protective skin barrier.
Also known as "allergy shots," allergen-specific immunotherapy is a series of injections that expose the pet to increasing doses of the purified allergen. The injections are specifically formulated to match each patient's allergy triggers. They are given at regular intervals over a year or more. Immunotherapy shots train the immune system to tolerate the pet's allergens, leading to decreased inflammation and itch (6). In turn, the need for symptomatic treatments and antibiotics is reduced.
The Take-Home Message
Environmental allergies in dogs and cats can be frustrating for pet owners and veterinarians to manage. The diagnosis and management of this chronic condition require a good deal of commitment from all involved. Dog and cat owners are more likely to effectively manage their pets' allergies when realistic expectations for treatment durations and outcomes are communicated. Fortunately, a wide variety of treatment avenues are available and provide excellent comfort to affected pets.
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Marsella R, Segarra S, Ahrens K, et al. Topical treatment with sphingolipids and glycosaminoglycan for canine atopic dermatitis. BMC Vet Res 16, 92(2020).
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Fischer NM, Muller RS. Allergen-specific immunotherapy in canine atopic dermatitis: an update. Curr Derm Rep 2019;8:296-302.
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