Introduction: Pets with allergies to pollen, grass, or dust are affected with atopic dermatitis, or atopy. People with allergies have symptoms such as runny eyes and sneezing, but animals with allergies more commonly show symptoms such as scratching, licking of the feet, and recurrent skin and ear infections. These symptoms can occur only during certain seasons, if the main offending allergens are seasonal pollens, but can occur all year round if the allergens persist in the environment year round (such as housedust mites and human dander). Atopic dermatitis typically starts in dogs between the ages of 6 months to 5 years, and can occur at any time of life in cats. In dogs, there is an increased incidence of allergies in certain breeds such as terriers, Cocker spaniels, Labradors, golden retrievers, Shar peis, and German shepherds, but any dog breed can be affected. The diagnosis of atopy is made by considering the symptoms, seasonality, and response to medications, and by ensuring no other similar itchy skin diseases such as food allergy, skin parasites, or skin infections are present. Once the clinical diagnosis of atopy has been made, the treatment options include treatment of allergic symptoms with topical and oral medications, or to perform allergy testing and desensitization injections to treat the underlying cause of the itching.
Symptomatic Allergy Treatment: Allergic animals with mild or very seasonal symptoms can often be managed by just using medications to treat their symptoms. Symptomatic medications include topical products such as shampoos, conditioners, and sprays, as well as oral medications such as antihistamines, fatty acids, steroids, and cyclosporin.
Topical products: Shampoos, conditioners and sprays used for allergies usually contain ingredients that help reduce itching such as oatmeal, topical anesthetics, antihistamines, or steroids. Allergic dogs benefit from frequent bathing not only because of the anti-itch ingredients, but because bathing helps to reduce allergens that are accumulated on the skin and coat. Antibacterial shampoos, conditioners and sprays (ie. chlorhexidene), can be helpful to reduce bacteria on the skin and are often used to help treat and prevent skin infections common in allergic dogs. Due to animals’ skin pH differences from humans, shampoos designed specifically for pets should be used. Weekly bathing and daily rinses or wipedowns with a wet washcloth are usually recommended. It is important that the shampoos be gentle (avoid tar and benzoyl peroxide products unless the dog is very greasy) so that the skin and coat do not become dry. Topical products that contain steroids (such as hydrocortisone, betamethasone, and triamcinolone) should be used carefully, as excessive use of topical steroids can predispose a pet to skin infections, and can cause the skin to become excessively thin or create blackheads.
Antihistamines: Oral antihistamines (such as benadryl, cetirazine, chlorpheniramine, and hydroxyzine) are helpful to reduce itching in 30-40% of allergic pets; they are not as potent as steroids, but also do not have unwanted steroid side effects. No antihistamine is better or more potent than another, and multiple antihistamines often must be tried to find the best one for each individual pet. They also need to be consistently given two to three times daily for benefit, and the dose requirements for pets are usually higher than for people, so it is important to ask your veterinarian about the right dose for your pet. In some pets, side effects can occur such as sleepiness or excitation. When buying over the counter antihistamines, it is very important to select products which do not contain pain killers or decongestants. Antihistamines may not be appropriate if pets have certain medical conditions such as seizures, glaucoma, hypertension, or urinary retention.
Fatty acids: Omega 3 and 6 essential fatty acids are derived from sources such as fish oil, flax oil, and vegetable oils, and they have mild anti-inflammatory effects on the skin (omega 3), as well as help to decrease skin dryness and improve the epidermal skin barrier (omega 6). They have to be given for 1-3 months before a beneficial effect is seen. An oral mixture of omega 3 and 6 fatty acids appears to be ideal for treatment of allergic dermatitis in dogs, and there are multiple combination products manufactured for pets, available in capsule, powder, liquid, or chewable tablet form. Fatty acids also work synergistically with antihistamines to help reduce allergic skin inflammation and itching. They may not be appropriate for use in pets with other medical disorders such as pancreatitis or clotting problems. The suggested dose of fish oil for allergic dogs is 180 mg EPA/10#. Improvement of epidermal ceramides (the skin lipid barrier) may occur by feeding a diet rich in the omega 6 fatty acid linoleic acid. Feeding pets a diet already enriched in essential fatty acids (such as Royal canin Skin Support, Hill’s J/D, or Purina DRM) is actually an easier and more effective way to deliver the appropriate doses and balanced ratios of fatty acids.
Topical Lipids: Recent research has shown that a major contributing factor for atopic dermatitis in humans and dogs is an abnormal skin barrier. Defective lipids in the skin increase the dryness of allergic skin and allow increased penetration of allergens through the skin layers. In addition to oral fatty acid therapy, several topical lipid replacement products have been developed for animals. Dermoscent Essential 6 spot on contains linoleic acid, Douxo brand spot ons, sprays, and shampoos contain phytosphingosine, and several shampoos and sprays made by Dechra Veterinary Products contain ceramides. Although more studies are needed in dogs, preliminary investigations of these topical therapies have shown encouraging improvements in symptoms as well as decreased skin dryness in treated animals.
Steroids: Injectable or oral steroids such as cortisone or prednisone have many pros and cons in the treatment of allergies in pets. They are inexpensive and work quickly and effectively to reduce itching, and for short term use they are relatively safe. However steroids have numerous side effects, such as increased thirst, increased urination, increased hunger, and weight gain. With prolonged use at high doses, steroids cause liver enlargement and increased liver enzymes, and can cause high blood pressure and kidney disease, weakened muscles and ligaments, infections of the skin and bladder, and thinning of the skin and hair loss. Animals that are treated with long-term steroids should have physical examinations, bloodwork and urine testing regularly to monitor for side effects, and other options to treat their allergies and to reduce their dependence on steroids should be tried.
Non-steroidal immune modulators/ immunosuppressants:
Cyclosporin (brand name Atopica) is an oral medication which can be used as a non-steroid way to reduce allergic skin inflammation and itching. It is more expensive than steroids and is helpful in approximately 80% of allergic dogs to control itch. Cyclosporin is given orally daily for 4-6 weeks, then the dose and frequency is slowly decreased to the lowest possible dose needed for comfort (some dogs need it daily, and in some the dose can be reduced to every 2-3 days). Cyclosporin has fewer side effects than steroids, but because it is still an immunosuppressive drug (it is the same medication used to prevent organ transplant rejection in humans), regular physical examinations with bloodwork and urine testing should be performed in pets on long term treatment. Potential side effects include vomiting and diarrhea, and more rarely skin or internal infections and benign growths on the skin or gums.
Apoquel (chemical name oclacitinib) is a new oral medication licensed for the treatment of both acute allergies and chronic atopy in dogs >12 months of age. It can be used instead of steroids to treat dogs with occasional seasonal pollen or flea allergy flares, and to control itch in allergic dogs while the underlying cause of the itch is addressed (ie. while a hypoallergenic diet trial is started in food allergic dogs, or to control itch in atopic dogs while allergy desensitization therapy has time for effect). This drug is a janus kinase inhibitor, similar to the human rheumatoid arthritis medication Xeljanz. Apoquel acts to reduce production of inflammatory allergic proteins and also to reduce the sensation of itch transmitted by nerves, which no other drug does. It is intermediate in cost between steroids and cyclosporine, and acts very rapidly (within hours) to reduce itching. It is given twice daily for 2 weeks, then once daily, and in both short term and longer term (2-3 year) studies appears so far to have very few side effects (occasional GI upset). Since this is a new drug, and since it does affect the immune system, regular examinations and labwork are still recommended.
Allergy Testing and Desensitization: Allergy testing is performed in atopic pets NOT to make a diagnosis of allergies (remember, the diagnosis of atopy is made by symptoms, response to medications and eliminating the possibility of other itchy skin diseases such as food allergy or skin parasites/infections), but to indicate which allergens are to be included in a hyposensitization vaccine. Allergy testing and hyposensitization injections (immunotherapy) are appropriate in animals with allergic symptoms that last longer than 2-3 months/year, and in pets in which the symptomatic therapy for allergies is not helpful, or which need steroids longer than 2-3 months/yr. Allergy testing can be done with a blood test (which is more convenient and can be performed by most primary care veterinarians, but may be less accurate than skin testing), or by intradermal/skin testing (usually performed by veterinary dermatologists, requires a light sedative and shaving, considered the “gold standard” of allergy testing. Allergy hyposensitization injections are given every 1-4 weeks (the dose and frequency of the vaccine are different for every pet), and are helpful in 70-75% of allergic pets to reduce symptoms and needs for medications. Sublingual (drops given orally under the tongue once or twice daily) allergy hyposensitization is also newly available, and appears in preliminary investigation to be similar in effectiveness as injectable allergy immunotherapy (Click on this link for more information). Allergy immunotherapy is usually a lifelong treatment and the degree of response to therapy varies with each individual animal; some pets only need the hyposensitization vaccine, some still need some symptomatic medications such as antihistamines, and some still need steroids, but at lower doses, less often or only during certain seasons. Allergy hyposensitization injections address the cause of a pet’s itchy skin by changing/calming down the hyperactive immune response to the environmental allergens, but require time (2-12 months) for effect, so symptomatic medications are continued while immunotherapy has time for effect.
Summary: Although allergies in pets are not “curable”, they are very treatable and controllable in most pets. Every animal is an individual and often different medications need to be tried or combinations of medications may need to be used for maximal comfort. When the motivated pet owner, family veterinarian and a veterinary dermatologist work together, our allergic pets can be helped to live long, comfortable lives.