Dog scratching

Atopic dermatitis (AD) is the term used to describe environmental (indoor and/or outdoor) allergies. It is a common problem in dogs and cats that can cause a significant amount of misery in affected animals. Allergies are unlikely to be cured, but with a thorough investigation including diagnostics, proper treatments and owner compliance, allergies can be managed. Proper management can make an animal very comfortable and allow it to live a normal quality of life. In addition to traditional injectable immunotherapy (allergy shots), oral immunotherapy is now an option.

But before we discuss treatments, let’s first take a quick look at what we know about allergies and atopic dermatitis in pets.

The Great Outdoors — and Indoors — Can Be Triggers

Common allergens that cause AD include tree, grass and weed pollens; human and animal danders; storage and dust mites; mold spores, wool, dust and insects. These allergic substances are usually absorbed through the skin but can also be inhaled. Unlike humans, animals rarely have a runny nose, tearing eyes or respiratory signs. Instead, allergies in pets are usually expressed in the skin, and affected animals will itch, lick and/or chew themselves. The skin may be red, irritated or thickened from the chronic trauma and left susceptible to secondary infection. The ears may be affected as well. These allergies may start at any age, but they usually develop within the first three years of life or after a recent relocation/move. Allergies may start as a seasonal problem, but then can develop into an all-year-round issue. Atopic dermatitis is a heritable disease and is more commonly reported in certain breeds of dogs (e.g., terriers) and cats (e.g., Abyssinians).

Common Signs of Allergy

Animals diagnosed with AD may be pruritic (itchy) in many regions of their body. The main areas affected include the feet (between the toes), ears, groin, armpits, legs, under the neck and the abdominal area. One or all regions may be affected. Atopic (allergic) animals usually have seasonal itchiness, but this may progress to a year-round concern. The ears may also be affected and can become itchy, red, painful, and malodorous with excessive debris and wax buildup. Clinical signs may wax and wane on a daily, weekly or even monthly basis as different things in the environment are exposed to the pet. The clinical signs are due to a certain threshold of allergens that, once reached, causes flare-ups. Secondary bacterial and yeast skin infections are very common and can become a recurrent problem.

Diagnosis Is Not Simple

Atopic dermatitis is a diagnosis of exclusion and several findings are required to make the diagnosis. A simple blood or skin test is not sufficient because clinically normal animals may also have positive findings on these tests. All results must be interpreted in the context of each individual case. Also, since the itchy skin commonly found with atopic dermatitis mimics other itchy skin diseases, potential causes must be ruled out and/or comanaged (for example—food allergies, flea allergy dermatitis, metabolic diseases, other external parasites such as mites, etc.). Information suggestive of atopic dermatitis includes the distribution of lesions, seasonality, and response to certain medications (antihistamines, corticosteroids, shampoo) and/or special diets. Allergy testing (skin testing and/or blood testing) may be indicated. The primary reason for these tests is to determine which allergens should be avoided and to determine what should be incorporated into the pet’s immunotherapy medication. This medication has traditionally been administered in injection form, but now oral immunotherapy is an option.

Management

Management of atopic dermatitis is different for each individual animal. Unfortunately, not all animals respond to all treatments, and usually a combination of treatments and medications are needed to control the condition. Management usually includes topical treatments to help decrease the degree of itching by removing allergens, yeast and bacteria on the skin. Sometimes corticosteroids, antihistamines, cyclosporine, tyrosine kinase inhibitors, and/or omega-3 or omega-6 fatty acid supplementation are used to help reduce inflammatory responses to allergens.

Allergen specific immunotherapy has been considered the "gold standard" for more than 40 years. “Allergen specific” means that, depending on the results from allergy testing, an allergy serum for desensitization/hyposensitization can be created for each individual patient. The allergens are combined at an optimal concentration and then administered at incremental amounts and strengths. The allergen combination is administered at a gradual taper in frequency of administration (for example, every other day, then weekly, then every other week, and then monthly).

Injectable allergen specific immunotherapy has about a 60 percent to 70 percent beneficial response rate, and usually takes 8 to 12 months to achieve desired results. Until recently, administration of the allergen serum was only available by injections under the skin. Now, oral immunotherapy (allergy drops) has become much more readily available for dogs and cats. These drops are administered under the tongue twice daily for at least a year. Because of where the allergen serum is applied, this is technically referred to as sublingual immunotherapy (SLIT).

Oral Immunology: A Great Option for Some Pets

SLIT has been available and used for humans with successful results for at least 50 years. The concept is virtually the same as the injections but formulated slightly differently to promote oral absorption and palatability. Early evidence indicates that at least 60 percent of patients have a favorable response. Also, at least half of dogs that responded poorly to the injections are reported to have successfully responded to the oral option.

As with any treatment option for AD, there are pros and cons to the oral immunology option. The advantages seem to be the safety (rare side effects) and ease of administration (no needles), as well as a potentially quicker response (3 to 6 months). These medications are also able to be stored at room temperature. The most noteworthy concern is that oral immunotherapy must be administered twice daily every day, so compliance for owners is difficult. Also, if the patient is "head-shy," this may not be the best option. The medication cannot be administered in food, as the allergy drops must have direct contact with the areas under the tongue in order to work. The dose may need to be decreased if clinical signs get worse and oral itching has been suspected (transient) for some patients. A pet can be started with one form and switched to another if necessary.

Long-Term Outlook

AD is a progressive disease that is almost never cured but is usually controlled with proper and consistent management. Control of the clinical signs can sometimes become frustrating to the pet and/or owners, but this can be avoided with regular checkups, good communication with your veterinarian, and compliance with the therapies prescribed. Flare-ups are common, and treatment protocols will likely be modified when necessary. Most pets with atopic dermatitis can live normal high-quality lives once managed properly!