Cat Atopy

Introduction

Atopy, also called allergic inhalant dermatitis and atopic dermatitis, is a clinical syndrome involving immune-mediated hypersensitivities to one or more normally innocuous environmental allergens that are either inhaled or absorbed through the skin.

How Atopy Affects Cats

Atopy is thought to be a genetically-influenced disorder causing cats to become hypersensitive to things that normally would not cause an allergic reaction. The mode of inheritance is not known, and factors in addition to heredity may well influence the development of the disease. The hallmark of feline atopy is intense and chronic itching, scratching, licking, biting, chewing and hair loss, which can be seasonal or non-seasonal and tends to affect the feet, face, ears and underbelly. Atopy can be associated with self-trauma and secondary skin infections, although this is less common in cats than in dogs. Atopic cats are prone to developing respiratory tract disease that mimics feline asthma. They also often develop symmetric hair loss and other skin lesions not typically seen in affected dogs. Recurrent malodorous ear infections are frequently seen in cats with atopy. Cats with seasonal atopy often develop chronic, non-seasonal disease as they age.

Causes & Prevention

Causes of Atopy in Cats

As mentioned above, atopy is a genetically-influenced abnormal reaction to contact with normal things. Common suspects include pollen, grasses, weeds, trees or other plants, mold, household cleaners, dust mites, animal dander, chemicals, kitty litter and countless other environmental allergens. There is no clear sex or breed predilection for feline atopy. Clinical signs of atopy normally are evident between 6 and 36 months of age.

Preventing Atopy in Cats

As with other hypersensitivity reactions, atopic reactions can be prevented by eliminating or at least minimizing the cat's exposure to the inciting allergens. These can be identified through intradermal allergy testing if they are not otherwise obvious. Other prevention techniques include minimizing other causes of itchiness (fleas, ticks, food allergies, etc.), so that the itchiness caused by the atopic reaction is not compounded.

Special Notes

There is no simple diagnostic test for feline atopy. Instead, a diagnosis of atopy is based upon the nature of the cat's clinical signs, its history and its response to treatment. There are a number of possible treatments for atopy, but the "right" treatment protocol depends upon the cause of the condition, the cat's overall health and the severity of its symptoms. Feline atopy cannot be "cured." Fortunately, it normally can be controlled with medication, diet and life-style management. Atopy is not life-threatening but does require life-long management to maintain a good quality of life for affected animals.

Symptoms & Signs

Atopy, also known as allergic inhalant dermatitis and atopic dermatitis, is an immune-mediated inflammatory and pruritic allergic disease which affects the skin and respiratory system of cats. The symptoms of atopy normally begin between 6 and 36 months of age and generally worsen as the cat becomes older. Atopy also tends to worsen during the spring and summer months in the United States, although over time it can become chronically non-seasonal. The hallmark of feline and canine atopy is intense pruritus (itchiness). However, atopy is much less commonly diagnosed in cats and the characteristic signs in cats differ somewhat from those in dogs.

Symptoms of Atopy in Cats

There is no reported gender or breed predilection for atopy in cats. The most common clinical signs of feline atopy are intense itching, scratching, licking, biting, chewing and hair loss around the feet, face, ears, tail base and underbelly. In cats, atopy also tends to manifest with symmetric alopecia (hair loss), miliary dermatitis or one of several eosinophilic granuloma complex lesions (these are eosinophilic plaques, eosinophilic granulomas and indolent ulcers, the description of which is beyond the scope of this article). Self-trauma, sores and scabs followed by secondary bacterial or yeast infections occur, but less frequently in cats than in dogs. In addition to these cutaneous signs of pruritis, many atopic cats develop recurrent or chronic otitis (ear infections). Their ears can become swollen and inflamed, itchy and irritated, and in many cases develop a nasty odor accompanied by profuse amounts of ear wax. Atopic cats also tend to develop respiratory symptoms which mimic feline asthma. Most clinical signs of feline atopy worsen with time.
True immune-mediated atopy in cats cannot be "cured," but it can be controlled with appropriate medical management and identification and removal of the inciting allergens.

Treatment Options

Atopy, also known as allergic inhalant dermatitis or atopic dermatitis, is a clinical syndrome in cats that involves immune-mediated skin and respiratory allergic reactions with a strongly suspected hereditary component. The most consistent clinical sign of atopy in both dogs and cats is pruritis – intense itchiness – which can lead to self-trauma, hair loss, weeping sores and behavioral changes. Unlike dogs, affected cats frequently also develop respiratory symptoms, symmetric hair loss and other cutaneous lesions in addition to pruritis.

Treating Atopy in Cats

The therapeutic goals for feline atopy are to eliminate or at least minimize the cat's exposure to the causative environmental allergens and thereby enhance its comfort and overall quality of life. The appropriate treatment protocol will depend upon the underlying cause of the particular cat's condition. Key factors include the nature and intensity of clinical signs, seasonality of those signs, distribution and severity of associated skin lesions, patient acceptance of treatments, client compliance with the time, effort, regularity and expense of lifelong treatment and other cost considerations. Most atopic cats can be treated on an outpatient basis. Owners need to know that this is a progressive disorder that rarely goes into remission and cannot be cured. There is no one "cookie-cutter" treatment program for feline atopy.
The pruritis associated with acute-onset and mild cases of atopy typically can be treated with oral antihistamines and omega-3 and/or omega-6 essential fatty acid supplements. Antihistamines can cause drowsiness, lethargy, anorexia, vomiting, diarrhea and even nervousness, so owners should watch for these possible side effects in affected cats. If sores or secondary bacterial skin infections are present, oral antibiotics can be prescribed. Shampoos and other topical treatments also are available to help control fungal, yeast and bacterial skin infections.
In severe or chronic cases of feline atopy, corticosteroid therapies are available and typically are quite effective for controlling the itchiness associated with environmental allergies and breaking the itch-scratch cycle. However, long-term steroid use can cause a number of adverse side effects, and steroid treatments should be tapered to the very lowest dosage necessary to control the condition. Often, steroids are prescribed to provide short-term relief until the clinical signs of atopy are brought under control. A combination of corticosteroids and antihistamines has been shown to control pruritus much more effectively than either steroids or antihistamines alone, and at much lower doses.
Cyclosporine, an immunosuppressant drug, is also available to help control the pruritis associated with severe or chronic atopic dermatitis in cats. This medication is expensive and has common side effects including vomiting, diarrhea, gingival hyperplasia, hypertrichosis (excessive hairiness) and pyoderma (pimples, acne, other purulent skin lesions).
In some cases, allergen-specific immunotherapy (also called hyposensitization) can help cats suffering from atopy. This form of treatment involves subcutaneous administration of a gradually increasing dose of allergens that are present in the cat's environment and that cause positive reactions on intradermal allergy skin tests. This therapy is helpful in the majority of cases in dogs and, while its efficacy in cats has not been established, it is thought to be similar to that in dogs. Hyposensitization normally is used when the cat has non-seasonal atopy and when anti-inflammatory treatment is not effective, causes unacceptable side effects or does not provide sufficient relief. Physical restraint by use of Elizabethan (cone) collars, foot bandages, T-shirts or sweat shirts may be helpful in reducing self-inflicted trauma, although they will not reduce the itchiness that predisposes affected cats to self-trauma. There are a number of topical treatments that can decrease pruritus. Even a warm bath can relieve itchiness by simply rehydrating the skin.
Owners of atopic cats need to understand that the environmentally-caused allergies are likely to affect their cats for life. However, with good owner compliance and individualized treatment, most cases can be well-managed. Routine veterinary examinations, at least twice a year, are important to long-term control of this condition, especially for cats on long-term steroid therapy.