Atopy (Allergies) in Dogs

Overview of Dogs with Allergies

Atopy is a pruritic (itchy) skin disease of dogs caused by an allergy to substances in the environment contacted through the air, either by absorption through the respiratory tract or contact through the skin. Atopy is thought to be an inherited disease. It is the second most common allergic skin condition in dogs; only flea allergy dermatitis is more common.

Symptoms of atopy usually begin relatively early in life, often by one year of age. Symptoms usually are seasonal at first, with most dogs showing clinical signs in the summer months when airborne allergens (such as plant pollens) are present in higher concentrations. As atopic dogs age, their symptoms tend to become less seasonal as they become allergic to more substances. Eventually, their itchiness can occur year-round.

Dogs with atopy are usually itchy, particularly the hands and feet. The skin may be red and irritated due to scratching, and the ears may also be inflamed. The symptoms of food allergy are difficult to distinguish from those of atopy.

What to Watch For

• Chewing at the paws
• Scratching the muzzle or rubbing it on the ground or with the paws
• Scratching the ears
• Shaking the head

Diagnosis of Canine Atopy

Diagnostic tests are necessary to rule out other skin diseases and support the diagnosis of atopy. These tests may include:

• A complete medical history and thorough physical examination, especially checking the ears and the skin of the face and paws. Often, abnormalities may not be detected on the physical examination of dogs with atopy. Occasionally, redness between the toes or around the muzzle of the face is the only finding.
• Skin scrapings to eliminate other diagnoses such as demodectic or sarcoptic mange (caused by mites).
• Fungal culture to rule out ringworm (also called dermatophytosis).
• Skin testing (or occasionally blood testing) to determine specific allergens to which your dog may be allergic.

Treatment of Canine Atopy

Initial treatments may alleviate symptoms, but do not treat the underlying cause of the allergy. Immunotherapy (allergy shots that work by modifying your dog’s immune response to allergens) is considered the best treatment for moderate to severe or long-standing cases of atopy.

Your veterinarian may recommend the following for your dog:

• Antihistamines
• Fatty acid supplements
• Antibiotics to treat secondary bacterial infection of the skin (called pyoderma)
• Soothing shampoos
• Corticosteroids (cortisone-like drugs such as prednisone) are very effective at reducing the symptoms of atopy, but they have many potential side effects that limit their long-term use. They should be used cautiously in the treatment of dogs with atopy.
• Cyclosporine (Atopica®, Cyclosporine capsules, USP)
• Oclacitinib (Apoquel)
• Lokivetmab (Cytopoint)

Home Care

• Atopy cannot be cured, and most dogs require some form of therapy throughout their lives. You will need to administer any medications prescribed by your veterinarian and avoid offending allergens as much as possible. Skin testing (also called allergy testing) can be performed to identify the specific substances to which your dog is allergic. As time goes by, however, most dogs with atopy become allergic to more and more allergens, making avoidance impractical in the long run.
• You should practice strict flea control. Other itchy (pruritic) skin diseases such as flea allergy dermatitis may have an additive effect on your dog’s skin condition.
• Observe your dog for rashes and worsening of any skin lesions. Secondary bacterial infection of the skin (pyoderma) is common in dogs with atopy and can contribute to their discomfort.

Preventive Care

Atopy may be an inherited disorder in dogs. Since environmental exposure to allergens is important in the development of disease, it cannot be prevented. Airborne allergens, such as plant pollens, are difficult to avoid, and there is little that can be done to prevent the development of atopy in a predisposed individual. Dogs that grow up in low allergen environments (dry climate with high elevation) may be less likely to develop symptoms.

Managing atopy in your dog takes some patience. However, by combining different methods of therapy, paying attention to your dog’s environment as well as you can, and observing your pet so that you can begin treatment as early as possible, you can make your pet feel their best.

Information In-Depth on Atopy in Dogs

Many skin diseases of dogs feature pruritus (itching) as a symptom and may resemble atopy. Ruling out other causes of pruritus is an important part of establishing a diagnosis.

Diseases that can resemble atopy include:

• Food allergies in dogs commonly cause a pruritic skin condition. As with atopy, dogs with food allergies often chew their feet, rub their faces, and scratch their ears. Thus, the symptoms of food allergy are virtually indistinguishable from those of atopy. One important historical difference to remember is that atopy symptoms usually begin between one and four years of age, whereas food allergy can begin at any age. A dog with an onset of signs that is less than eight months of age or over six years of age, is unlikely to have atopy. Also, atopy is usually well controlled by treatment with corticosteroids (hormones) like prednisone. Food allergy is variably responsive to prednisone; only about 50 percent of affected dogs will respond.
• Flea allergy dermatitis is the most common allergic skin disease seen in the United States. Like food allergy, it is variably responsive to corticosteroids. Dogs with flea allergies tend to chew and scratch at their back ends, so lesions are typically seen over the rump, on the belly and between the hind legs. This difference helps to differentiate this disease from atopy.
• It is possible, however, to see atopy and flea allergy in the same animal.
• Scabies is an itchy skin disease of dogs caused by the sarcoptic mange mite. Affected dogs are extremely itchy and often have lesions on their ears, elbows, and hocks. Lesions may also be seen elsewhere on the dog. This disease is poorly responsive to treatment with corticosteroids.
• Pyoderma (bacterial infection of the skin) is often associated with atopy and other pruritic skin diseases. Chronic self-trauma to the skin breaks down normal defense mechanisms and allows colonization by bacteria leading to infection.
• Infected skin can be very itchy. Some animals with atopy are only mildly itchy most of the time but may be much worse when they have pyoderma. Less commonly, yeast infections of the skin may be seen secondary to atopy and can also cause the animal to be itchy.

Diagnosis In-Depth on Allergies in Dogs

Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnostic tests are necessary to rule out other skin diseases, as well as to support the diagnosis of atopy. These tests may include:

• Your veterinarian will get a complete medical history of your dog. Expect to be asked about the age of onset, whether the problem is or was at one time seasonal, and where your dog chews and scratches. Bring a record of which medications your pet has previously been taking and be prepared to answer questions about how effective they have been.
• Your veterinarian will perform a complete physical and dermatological examination. Included in the exam of the skin should be a careful exam of the feet, pads, and claws. There will also be special attention paid to the ears. Atopy will sometimes present itself as recurring external ear infections without any other skin symptoms.
• A skin scraping will be done to help rule out scabies. Since these mange mites are notoriously difficult to find, your veterinarian may recommend a trial treatment for scabies to completely rule this disease out, especially if there is ear involvement. Atopy and scabies both commonly show ear symptoms.
• A fungal culture is often taken to rule out dermatophytes (ringworm fungi). Dermatophyte infections in the skin can mimic the symptoms of many skin diseases and thus, a culture is frequently a part of the diagnostic process.
• A food trial may be done to rule out food allergy. During a food trial, your dog is fed food containing ingredients that it has never been exposed to before as its only source of food for six to 12 weeks. If the symptoms don’t improve, food allergies can be excluded.

Once the above diseases have been ruled out, a presumptive diagnosis of atopy is made. Allergy testing is then performed to identify allergens to which your pet is sensitive. Intradermal allergy testing (skin testing) is done to determine which allergens will cause a reaction. The hair is clipped from one side of the thorax and small amounts of many individual allergens are injected into the skin. Light sedation may be necessary to allow proper restraint during the procedure. This test usually requires a referral to a veterinary dermatologist, which may necessitate travel to the nearest specialty practice. Your pet must be off all medications prior to testing so that the skin will react. Reactions to allergens in cat skin are subtler and therefore, more difficult to read.

There is a blood test available for dogs to test for allergens by measuring the levels of IgE antibody to different allergens that are present in the bloodstream. IgE is the type of antibody that is involved in the allergic response. The advantage of this test is the convenience for the pet owner and the veterinarian. A blood sample is sent to one of several commercial laboratories. There is no need to travel to a dermatologist or to withdraw medications. However, false positive results are often a problem, and this test is considered less reliable than skin testing. More accurate blood tests are being developed and this technique may be more viable in the future.

Allergy Treatment In-Depth

Two primary forms of treatment for atopy are available: drug treatment and immunotherapy. The ideal treatment for most moderately and severely affected dogs is some combination of both types of treatment. Drug therapy relieves the symptoms of atopy but does nothing to treat the underlying allergy itself. Most dogs with atopy are young and may require years of therapy.

Treatments for canine atopy may include one or more of the following:

• Antihistamines are much less helpful in atopic dogs than they are in humans. Antihistamines help only 25 to 30% of atopic dogs but are often tried first because they have fewer adverse effects than the cortisone-like drugs. Some animals respond better to one antihistamine than others, and your veterinarian may try 2 or 3 different types of antihistamines before concluding that they are not helpful in a given dog.
• Fatty acid supplements may relieve itchiness by modulating the immune response. Certain fatty acids such as eicosatetraenoic acid (found in fish oil) help change the chemical composition of cell membranes and ultimately the types of chemical mediators produced during the allergic response, resulting in a milder response. Like antihistamines, these products are not helpful in all affected animals, but they are very safe. Some dogs that do not respond well to antihistamines may respond to a combination of antihistamines and fatty acids.
• Secondary bacterial infections are common in dogs with allergic skin disease. Therefore, dogs with atopy occasionally need antibiotics to treat complicating pyoderma. Yeast infections of the skin and ears also must be treated occasionally.
  Shampoo therapy may be very helpful in managing itchiness caused by atopy. Shampoos that contain colloidal oatmeal are soothing and moisturizing and can be used frequently without drying the skin. Some oatmeal-based shampoos contain topical anesthetics or topical corticosteroids that are very safe and further help reduce itchiness.
• When the above treatments are no longer effective, corticosteroids such as prednisone may be used. This class of drugs is very effective in atopic animals. Unfortunately, however, these drugs have many potential adverse effects that restrict their long-term use. Examples of the adverse effects of corticosteroids include increased water consumption and urinations, increased appetite and food intake leading to obesity, suppression of the immune system leading potentially to secondary infections, irritation of the stomach, alterations in liver function tests, and suppression of normal adrenal gland activity. Short-acting, orally administered corticosteroids are safer than long-acting injectable corticosteroids because the former can be cleared rapidly from the animal’s body in the event of adverse effects. Any dog that can be helped by long-acting injectable corticosteroids can be relieved just as effectively and with less risk by use of short-acting orally administered corticosteroids.
• Immunotherapy (hyposensitization, desensitization, allergy shots) theoretically is the ideal form of treatment for atopy and is recommended for dogs that cannot be managed safely and effectively with symptomatic therapy. The exact mechanism by which immunotherapy works is not well understood, but the goal is to induce tolerance by the immune system to allergens to which the animal is sensitive. This technique is effective in 60 to 80% of atopic dogs. An extract of the allergens selected by allergy testing is prepared. Initially, a small amount is injected frequently (every 1 to 2 days) and the dosage gradually increased. Due to the frequency of injections, your veterinarian will show you how to administer the injections at home. Once the cumulative dose reaches a certain level, the injection interval is slowly increased until injections are given every 2 to 3 weeks. The interval may be maintained for a long time. Improvement is gradual and your dog may not benefit markedly for the first 3 to 6 months of immunotherapy. Antihistamines, fatty acid supplements, and soothing shampoos may be used while immunologic tolerance develops.
• Another therapy includes use of an immunomodulatory drug called cyclosporine (Atopica®, Novartis). Cyclosporine has properties that fight against inflammation and itching. It is generally started daily and often decreases to every other day or every third or fourth day as clinical signs improve. It may take four to eight weeks to see improvement.
• A newer therapy called Oclacitinib (Apoquel) has been very effective in control of itching in dogs with allergies. This drug uniquely targets cytokines that are involved in the itch process. Onset of relief can be as early as 4 hours and controls the itch within 24 hours. Many veterinarians like this drug because it controls itching without the side effects of steroids.
• Lokivetmab (also known as CADI or Cytopoint) is a monoclonal antibody treatment that targets and deactivates canine IL-31. Canine IL-31 is a cytokine involved in sending the itchy signal to the brain. Therefore, Cytopoint® is effective at controlling pruritus (itching) in dogs with allergies. Because this drug focuses on canine IL-31, it is a dog only product.
• Cytopoint® is not effective in cats. Cytopoint® is not considered a corticosteroid or an antihistamine but has effects that can be similar and has been shown to be a great drug alternative to antihistamine drugs and steroids such as prednisone, dexamethasone, depomedtrol, and triamcinolone. Cytopoint® has been very effective in controlling itching without side effects. This has been very effective in dogs. Shots generally last from 4 to 8 weeks in most dogs.

Atopy is a disease that varies considerably in intensity depending on the individual animal and their present environment. Therefore, home monitoring and communication with your veterinarian is vital for success. Treatment is most likely to be effective if individualized to the dog.

Follow-up Care for Dogs with Allergies

Follow-up for canine atopy may include the following:

• Administer all veterinary prescribed medications as directed. Treatment often fails because medication is stopped when improvement is seen or when it is too soon for improvement to be expected. It is particularly important for you to administer your dog’s antibiotic prescriptions through to their completion and to be patient with immunotherapy.
• Immunotherapy should be tried for nine to 12 months before it is deemed truly unsuccessful.
• Observe dogs on immunotherapy for signs of increased itchiness after injections or for hives or swelling. Although uncommon, animals may react to the allergen extract. Alterations in the injection schedule may be helpful to alleviate these problems. Severe reactions (anaphylaxis) may be life threatening but are extremely rare.
• Dogs on immunotherapy may improve after injections but begin to itch before the next injection. Shortening the interval between injections may help. Always consult your veterinarian before making changes to the injection interval schedule.
• Schedules may become complex. Keep a log of how much extract was given and record the date.
• Observe for rashes, pustules, infected ears, or any other skin lesions that may occur secondary to itching. Flare-ups of these problems may occur while waiting for improvement and will need to be treated.
• Avoidance of allergens is usually impractical. However, air filters inside the home may be of some benefit.

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