Introduction
Atopy, also known as allergic inhalant dermatitis, atopic dermatitis and atopic eczema, is a common clinical syndrome that involves immune-mediated hypersensitivity (allergy) with a hereditary predisposition. The hallmark of canine atopy is severe pruritus, or itchiness, mainly of areas on the feet, face, and underbelly. It usually is associated with self-inflicted trauma from persistent scratching at the affected sites. Secondary skin afflictions are also common. Atopy is reported to be one of the most common allergic skin disorders in dogs, perhaps second only to flea bite hypersensitivity and possibly food allergies. Fortunately, most cases of atopy are treatable.
Treating Atopy in Dogs
The therapeutic goal for this disease is to eliminate or at least minimize exposure to the causative allergens and thereby reduce the dog’s discomfort. The appropriate treatment protocol will depend upon the underlying cause of the particular dog’s condition. Key factors include seasonality of the clinical signs, the distribution and severity of associated skin lesions, client compliance, and cost considerations. Most cases of atopy are treated on an outpatient basis. Owners must recognize that this is a progressive disorder that rarely goes into remission and cannot be “cured.” Lifelong treatment is usually necessary.
Acute-onset and mild cases of atopy can be treated with oral antihistamines and omega-3 essential fatty acid supplements. Together, these are reported to alleviate pruritus in up to 30% of cases. Antihistamines can cause drowsiness, lethargy, anorexia, vomiting, diarrhea, and even nervousness, so owners should watch for these possible side effects. If secondary bacterial skin infections occur, oral antibiotics can be prescribed. Shampoos and other topical treatments also are available to help control fungal, yeast and bacterial skin infections.
In especially severe or chronic cases of atopy, corticosteroid therapies can be used. Steroids are quite effective for controlling the itchiness commonly associated with environmental allergies and can help break the itch-scratch cycle. However, long-term steroid use can cause a number of adverse side effects, and steroid treatment should be tapered to the very lowest dosage necessary to control the condition. Often, steroids are only given temporarily to provide short-term relief until the clinical signs of atopy can be 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, which is an immunosuppressant drug, has 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.
In some cases, allergen-specific immunotherapy (also called hypersensitization) can help dogs suffering from atopy. This form of treatment involves subcutaneous administration of a gradually increasing dose of allergens that are present in the dog’s environment and that cause positive reactions on 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. 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 immunotherapy is usually slow, taking 3 to 12 months in most cases.
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 dogs 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 dogs with atopy need to understand that the environmentally-caused allergies are likely to affect their dogs for life. However, with good owner compliance and individualized treatment, virtually all cases 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 therapy.