Atopic disease is an itchy skin condition sometimes referred to as atopy, environmental allergy, inhalant allergy, or ‘hay fever’. It may occur in dogs, cats, and many other animals. In dogs, it is a common, often hereditary problem that can occur in any breed but especially terriers, retrievers, German Shepherds, Bulldogs, Pugs, Lhasa Apsos, Shih tzu’s, Boxers, Dalmatians, Spaniels (especially Cocker Spaniels) and Shar Peis. Cats have not demonstrated a clear breed predisposition.
Signs of Atopy in Dogs and Cats
The most common sign of atopy in dogs and cats is itching. This is seen as paw licking, leg chewing, face rubbing, armpit, belly and groin licking. Head shaking and ear infections are also very common. The coughing, sneezing, runny eyes that are common with human allergic reactions may occur, but are less frequent in animals. The allergens causing the symptoms may be inhaled or absorbed into the skin.
Cats can show any of the signs seen in dogs in addition to asthma. Cats sometimes show “miliary dermatitis” as the only noted problem (which may not always be itchy). Flea allergy (allergic reaction to flea bites/ flea saliva) often occurs with atopy. Flea allergy itching is usually focused on the rump, tail, groin and thighs. Animals with these allergies may ALSO be allergic to (or develop allergy to) certain foods (see Food Allergy handout). The scratching and inflammation associated with atopy often leads to secondary infections (bacteria, yeast or both) and seborrhea (dandruff) which create additional discomfort and malodor.
The typical history associated with an allergic pet is development of clinical signs between 6 months to 3 years of age. For approximately 50% of pets, the first few winters may be free of signs unless there is an allergy to house dust/dust mites/human dander or other indoor allergens. Allergies usually worsen with age, and can progress to year round in many patients. The other 50% of pets start with year-round clinical problems.
Diagnosis of Atopy in Dogs and Cats
Diagnosis is based on history, clinical signs and eliminating all other problems that can cause similar signs. This may be a time-consuming process. Confirmation of atopy is based on intradermal allergy testing or blood tests, however, these tests are not 100% and can not be used alone to diagnose atopy.
Allergies may be controlled, and less often cured. Treatment of allergic pets depends on the severity of clinical signs and the history of the patient. Avoiding items that cause allergies is ideal, but often difficult with environmental allergies.
Treatment of Atopy in Dogs and Cats
There are two basic treatment strategies for dealing with atopy in dogs and cats including preventative therapy and symptomatic therapy. Symptomatic therapy can be range from mild to very aggressive. In addition, it is important to treat secondary problems causes by allergies.
Preventative Therapy for Atopic Disease
Hyposensitization using an allergy vaccine is considered the safest/most effective therapy. This is the therapy of choice for most allergic pets. The downside is injections must be given all year long (usually done at home by the owner) or SubLingual ImmunoTherapy (SLIT) is used. The vaccine may require up to 12 months for full effect. Many pets show improvement during the first 4 months of treatment. This is usually continued as a life long therapy but 20-25% may become desensitized and discontinue therapy. The intradermal allergy test (IDAT) is performed to determine which allergens should be included in the allergy vaccine. Antihistamine and corticosteroid therapy interfere with skin testing, so antihistamines need to be stopped 10 days prior to skin testing, and most steroids need to be stopped 3-6 weeks prior to testing, depending on the type of steroid.
Allergy vaccine therapy is successful 60-70+ % of the time. Some pets still need additional symptomatic therapy during their worst time of the year. This is the only therapy that strives to desensitize and cure the allergy condition.
Symptomatic Therapy for Atopic Disease
- Antihistamines have few side effects and are effective 10-20% of the time. Multiple daily dosing is usually required in pets. Two week trials with each antihistamine are prescribed to determine which antihistamine is most effective for your pet.
- Fatty acid supplements also have few side effects and are effective 10% of the time. High dose omega-3 fatty acids are the most common form of neutraceutical supplementation for atopy. Fatty acid supplements are often more effective if used in combination with antihistamines and a lower fat diet.
- Bathing and topical therapy are also helpful to remove allergens, bacteria and yeast from the skin in addition to reducing seborrhea and malodor.
- Atopica® (cyclosporine) is a therapy for atopy that has been available for over a decade and is very effective (70%) and has limited side effects. Pets need to be rechecked periodically while on this medication (initially monthly then less frequently).
- Cortisone-type drugs (corticosteroids) are the most common nonspecific, anti-inflammatory, anti-itch medications used. These are also the most dangerous since they can have many unwanted, potentially life threatening side effects. Life long monitoring is required if using steroid therapy. This therapy should only be used for short periods or if safer options are not effective.
- Apoquel® (oclacitinib) has been available since 2014 for dogs over 12 months of age. It blocks signals in the immune system that are important to communicate allergy (and other messages). Monitoring is needed when on this medication.
- Canine Atopic Dermatitis Immunotherapeutic® is a new monoclonal antibody therapy administered by subcutaneous injection. It binds excessive IL-31 which is one of the important molecules signaling allergic itch in atopic dogs. This therapy is very safe but needs to be re-administered every 3-6 weeks as needed.
Treatment of Secondary Complications of Atopic Disease
Secondary bacterial and yeast infections must always be considered if an animal has had an allergy flare-up. If the infection is present, it may seem as if the medications used for the allergy are no longer effective. Microscopic cytology of skin samples need to be evaluated to determine if infections are present. If present, then anti-bacterial or anti-yeast medication must also be used along with the therapy to control atopy. Failure to address secondary infections can result in persistent clinical signs.