Dog Atopy

Introduction

Atopy is a clinical syndrome in which there is a hereditary tendency to develop immune-mediated hypersensitivities – or allergies - to normally innocuous environmental allergens that are either inhaled or absorbed through the skin. An allergen is simply any substance that is capable of causing an allergic or hypersensitivity reaction in a particular animal. In dogs, atopy is also known as allergic inhalant dermatitis, atopic dermatitis and atopic eczema. Atopy is one of the most common allergic skin diseases in domestic dogs, second only to flea bite dermatitis and followed closely by food allergies.

Causes & Prevention

Causes of Canine Atopy
As mentioned above, atopy is a genetically programmed abnormal reaction to contact with normal things. The mode of inheritance is not known, and certainly factors in addition to heredity probably influence the development of the disease. Common contributors to atopy include pollen, grasses, weeds, trees or other plants, mold, household cleaners, dust mites, insect bites, animal dander, chemicals and innumerable other environmental allergens. There is no clear sex or age predilection, although atopy does seem to be slightly more common in female dogs and in younger animals between 1 and 3 years of age. The age of onset can vary widely, and certain breeds are predisposed. There is marked geographic and seasonal variation in exposure to potential allergens.

Prevention of Canine Atopy
As with other hypersensitivity reactions, atopic reactions can be prevented by eliminating the dog's exposure to the offending allergens. Those allergens can be identified through veterinary allergy testing, if they are not otherwise obvious. Other standard prevention techniques include minimizing any known sources of itchiness (fleas, ticks, poison ivy/oak, certain components of the diet, etc.), so that the itchiness caused by an atopic reaction is not compounded.

Special Notes
Atopy cannot be cured in the traditional sense of the word. However, normally it can be controlled with medication, diet and life-style changes. Atopy is not life-threatening, but it does require management to facilitate a good quality of life for affected animals.

Symptoms & Signs

Introduction
Atopy is an extremely common, genetically-influenced disease that causes dogs to become hypersensitive to things that normally would not cause them to have an allergic reaction. Also known as allergic inhalant dermatitis, atopic dermatitis, "skin allergies" or atopic eczema, canine atopy is characterized by chronic itchiness (prurutis), which often is seasonal and typically affects the feet, face and underbelly. It commonly is associated with self-inflicted trauma from scratching or biting at the itchy areas. Secondary skin afflictions are also seen. Atopy can be so severe that it interferes dramatically with a dog's quality of life.

Symptoms of Atopy in Dogs
Owners of affected dogs may notice one or more of the following symptoms, which are the hallmarks of canine atopic dermatitis:

Itching, scratching and rubbing (intense, chronic, often seasonal; especially feet, face and underbelly)
Licking (intense, chronic, often seasonal; especially feet, face and underbelly)
Biting, chewing (intense, chronic, often seasonal; especially feet, face and underbelly)
Sneezing
Runny nose (allergic rhinitis)
Watery eyes (ocular discharge; excessive tearing)
Skin and coat discoloration (brownish-red) from salivary staining
Bumps, lumps, pustules on affected skin areas
Sores (raw, weeping "hot spots") from self-trauma
Deep scratches in the skin (excoriations)
Scabs; crusting of the skin surface
Greasy or flaky skin
Hair loss (alopecia)
Skin infection (from self-trauma and secondary bacterial infection)
Red, swollen, inflamed, irritated ears and ear flaps
Ear canal infections (otitis externa; recurrent; bacterial or yeast)
Dark, waxy ear exudates (profuse; often smelly)
Unpleasant, "yeasty" ear odor
Skin thickening and darkening in affected areas
In addition to the feet, face and abdomen, frequently affected areas include the base of the tail, the groin area, around the eyes, around and inside the ears, under the front legs (in the "armpits," called the axial area), between the toes (interdigital space), on top of the feet and on the muzzle. Most dogs first show signs of atopy when weed pollens become prevalent, in late summer and early fall. Additional tree and grass pollens and other environmental allergens become especially common in the spring. Of course, allergens inside the house, such as dust, wool, plant fibers, mold, feathers, mites, fleas, animal dander and the like, often contribute to year-round allergies in companion dogs. Unfortunately, most dogs with seasonal atopy eventually progress to having non-seasonal, year-round disease, and most symptoms of atopic dermatitis worsen with time. Atopy cannot be cured, but usually it can be controlled. If your dog suffers from these clinical signs, consider scheduling an appointment with your veterinarian as soon as you can.

Dogs at Increased Risk
There is no clear sex predisposition for atopic dermatitis, although it is slightly more common in female dogs. While the age of onset can vary widely, atopy is most frequently first seen in young dogs between 1 and 3 years of age. Certain breeds are more susceptible to the disorder, including the Chinese Shar-pei, Cairn Terrier, West Highland White Terrier, Boston Terrier, Boxer, Scottish Terrier, Sealyham Terrier, Lhasa-Apso, Shih-Tzu, Wire-Haired Fox Terrier, English Bulldog, Pug, Poodle, Dalmatian, Irish Setter, English Setter, Golden Retriever, Labrador Retriever and Miniature Schnauzer. However, any breed of dog, including mixed breed dogs, can suffer from this condition.

Diagnosis & Tests

Introduction
Canine atopy can be difficult to distinguish from flea bite allergies, sarcoptic mange (scabies), demodectic mange (demodicosis), food allergies and other skin and hair-loss disorders, making it somewhat difficult to diagnose. However, the dog's history, physical examination results, location of affected skin areas (lesions) and possible seasonality of symptoms can all lead to a suspected diagnosis of atopic dermatitis. Further tests can definitively diagnose the disorder.

How Atopy is Diagnosed
A dog that presents with pruritis (itching and scratching) and other signs of skin discomfort and disease will go through a thorough physical examination, including a dermatologic examination, at the veterinary clinic. Additional diagnostic tools include deep skin scrapings, microscopic analysis of plucked hairs (trichography), bacterial and fungal cultures, skin fine needle aspirate or biopsy with corresponding cytologic and histopathic examination of the skin samples, and dietary modification. Flea allergies, food allergies and adverse reactions to other external parasites must be ruled out to definitively diagnose atopy, because these conditions can complicate the diagnostic and treatment decision-making process. Bacterial, fungal and other skin infections, as well as cancer and behavioral disorders, must also be ruled out.

The most reliable form of advanced confirmatory testing is intradermal skin testing, which is very similar to the process used to diagnose specific allergies in people.

This is the gold standard for diagnosing environmental hypersensitivities, and should only be conducted after oral or injectable drug therapy has been stopped for an appropriate period of time, ranging from weeks to months. The veterinarian will inject directly under the patient's skin tiny amounts of substances known to commonly cause skin allergies in domestic dogs. After a certain period of time, she will evaluate the injection sites for any observable abnormal reactions. The process can be time consuming and costly. It can also be uncomfortable and even painful for the patient, as human patients can attest.

If intradermal testing is unavailable or impractical in a given case, there are several serum tests available to help the veterinarian identify possible causative allergens by identifying antibodies to those allergens in the dog's blood. These tests are more convenient, less expensive and less risky than intradermal skin tests. They also are less reliable in terms of their results.

Special Notes
Canine atopic dermatitis is one of the most frequent and frustrating skin diseases in companion dogs, for the owner, the veterinary team and the pet. However, with time and patience, it usually can be manageable for all involved.

Treatment Options

Introduction
Atopy is one of the most common allergic skin disorders in domestic dogs and is uniformly frustrating for owners and for their pets. It causes intense pruritis (itchiness), scratching and associated skin lesions, with secondary infections being common as well. Fortunately, with patience and persistence, most cases of canine atopy are treatable or at least manageable. The therapeutic goal for this disease is to eliminate or at least minimize exposure to the causative allergens and thereby eliminate the dog's persistent discomfort.

Treatment Options
The appropriate treatment protocol will depend upon the underlying cause of the particular dog's atopic condition. Key factors include seasonality of the symptoms, the distribution and severity of associated skin lesions, the presence of any secondary bacterial or yeast infections, client commitment and compliance and cost considerations. Most cases of atopic dermatitis can be treated on an outpatient basis. Owners should recognize that this is a progressive disorder that rarely goes into remission and cannot be cured in the ordinary sense of that word. Lifelong treatment or management usually is necessary to return the dog to an acceptable and comfortable quality of life. Unfortunately, most dogs have allergies to a number of different environmental factors, and it rarely is possible to identify and eliminate all of them from the dog's normal living circumstances.

One of the first therapeutic steps should be to remove any known or identifiable sources of itchiness other than atopy. These may include flea infestation, ticks, mites, lice, infection, food allergies or other skin irritants. Acute-onset and mild cases of canine atopy usually can be managed with oral antihistamines and with omega-3 essential fatty acid nutritional supplements, usually derived from fish oils. Together, these are reported to alleviate pruritus in up to 30% to 40% of affected dogs. Antihistamines can cause drowsiness, lethargy, anorexia, vomiting, diarrhea and sometimes nervousness, so owners should watch for these possible side effects. If secondary bacterial skin infections occur, oral and topical antibiotics can be prescribed. Yeast or fungal infections typically can be treated topically or orally as well. Shampoos and other topical treatments also are available to help control skin infections and to soothe and rehydrate inflamed, irritated skin.

In especially severe or chronic cases of atopy, corticosteroid therapies can be used. Steroids are probably the most effective medication for controlling the itchiness associated with environmental allergies and for breaking the itch-scratch-itch cycle. However, long-term steroid use also carries the most serious potential adverse side effects; steroid treatment should be tapered to the very lowest dosage necessary to control the condition. Often, steroids are given temporarily or intermittently, to provide short-term relief until the symptoms of atopy have been brought under control. Cyclosporine, which is an immunosuppressant drug, has also proven effective in controlling pruritus associated with severe or chronic atopic dermatitis. This treatment is quite expensive, especially for large-breed dogs. The most common side effects of cyclosporine are vomiting and diarrhea. A combination of corticosteroids and antihistamines has been shown to control itchiness much more effectively than either steroids or antihistamines alone, and at much lower doses. Topical preparations containing hydrocortisone and Pramoxine are often prescribed for isolated, irritated areas of skin. They are quite effective in providing temporary relief from itching and pain.

In some cases, allergen-specific immunotherapy (also called hypersensitization) can help dogs suffering from atopy. This treatment is usually reserved for those dogs that do not respond sufficiently to other forms of medical management. Hypersensitization involves a series of subcutaneous injections of gradually increasing doses of allergens that are present in the dog's environment and that cause positive reactions on the dog's intradermal allergy skin tests. This therapy is helpful in about 70% of the cases, as the dogs become desensitized to the environmental allergens over time (usually 9 to 12 months of treatment or longer). Hypersensitization normally is used when it is desirable to avoid or reduce the amount of steroids being given, when clinical signs last longer than 4-6 months despite other treatment, or when other forms of antipruritic therapy do not provide sufficient relief. The response to allergen-specific immunotherapy is usually slow, taking 6 to 12 months in most cases.

Physical restraint by use of Elizabethan (cone or "lampshade") collars, foot bandages, T-shirts, sweat shirts or canine booties may be helpful in reducing self-inflicted trauma, although they will not reduce the itchiness that predisposes affected dogs to chewing, licking, scratching and biting. Finally, dietary management can greatly reduce the symptoms of atopy in some dogs by switching to a higher-quality food, even in the absence of an identifiable food allergy.

Prognosis
Owners of dogs with atopy should recognize that environmentally-caused allergies are likely to affect their dogs for life. However, with patience, individualized treatment, good communication and cooperation between owners and the medical team, virtually all cases of atopy can be well-managed. Routine veterinary examinations, at least twice a year, are important to long-term control of this condition, especially for dogs on long-term corticosteroid or other pharmaceutical therapy.