NEW METHODS OF HELPING YOUR ITCHING PET
Spring has arrived, the weather is beautiful, the plants are growing, and your pet is itching. With all the joys Spring brings for us and our pets, it also is the time of year when skin allergy is at its worst. The last few years have brought some exciting new concepts in the treatment of skin allergy in cats and dogs.
What is skin allergy?
Skin allergy in pets includes several specific conditions which include: inhalant allergic dermatitis (also known as atopy), contact allergic dermatitis, fleabite hypersensitivity, and bacterial (staphylococcal) hypersensitivity. These conditions differ by which substances cause the allergy, and how the allergens enter the body. The reaction in the skin of the animal is similar regardless of the specific type of allergy.
The response of the skin to the allergen is inflammation. With inflammation four symptoms occur: redness, heat, swelling, and pruritis (itchiness). The owner usually notices the animal's response to inflammation, which includes persistent scratching, chewing, or rubbing of the skin. The pet, if a dog often develops a rash or weeping sores. This can progress to hair loss, pigmentation of the skin, thickening of the skin, and foul odor. The lesions in cats are different. Usually cats develop multiple small crusts (we call this miliary dermatitis). This can progress to hair loss (especially over the back), and sores (especially on the face).
What can be done to stop the problem?
With allergies, the best approach is to eliminate the source of the allergy. With some types of allergy, such as food allergy, this can be a simple matter of identifying the offending food and eliminating it from the diet. With other types of allergy, such as fleabite hypersensitivity, the offending agent can be eliminated, but much effort is required. Still other causes of allergy (allergens such as inhaled grass pollen or inhaled mold spores) are impossible to eliminate from the animal's environment.
If the cause can not be eliminated, then one can approach the problem in two distinct ways. One way is to treat the symptoms. The other is to desensitize the pet before the symptoms occur.
If the first approach is taken, the pet is often given medications such as corticosteroids (prednisone, etc.) to stop the itching caused by inflammation. A second medication often given is an antihistamine. Antihistamines work by blocking the attachment of histamine to cells that trigger inflammation. Antihistamines must be given before inflammation occurs to be effective. Another group of drugs used to treat skin allergy is the essential fatty acids. Certain fatty acids block inflammation by interfering with a group of chemicals known as prostaglandins. It is important to know which ones do this, since other fatty acids can promote prostaglandin production and make inflammation worse. Finally, there are many medications that can be applied directly to the skin to reduce inflammation directly, or indirectly by helping clear up complications of inflamed skin. These products come in many forms: shampoos, lotions, ointments, rinses, sprays, etc. They include topical anesthetics, soothing compounds such as oatmeal, corticosteroids, moisturizers, antibacterial compounds, etc. Which products to use is based on the Veterinarians assessment of the skin.
Atopica is a selective immune suppressant drug. It originally was used in transplant patients to help prevent rejection of the transplanted organ. It was tested and has been used at a much smaller dose to effectively treat dogs with atopic dermatitis. While prednisone has many potential long term adverse side effects, this has not been the case with cyclosporine. Some animals do have undesirable symptoms when Atopica is started. This can include gastrointestinal signs of vomiting or diarrhea; and much less commonly muscle cramps, loss of appetite, or inflammation of the gingival tissue of the mouth. These side effects reverse quickly if the medication is stopped. For the majority of dogs that do not develop these problems, Atopica can safely be used long term. Initially the medication is given every day for 4 to 8 weeks. Once symptoms have resolved, the frequency can be reduced to once every 3 to 4 days or sometimes even less frequently. If there is not a beneficial effect in 8 weeks the medication should be stopped.
The second approach has been made available by recent breakthroughs in allergy testing. At All Creatures Veterinary Hospital, we are currently using a blood test called a RAST test to identify which substances the animal is allergic to. We can test for inhalants (both indoor and outdoor), contact allergens, fleabite hypersensitivity, bacterial hypersensitivity, and food allergy. Such factors as when the allergy occurs (seasonal or not), where it occurs (indoors or outdoors), and what parts of the body are involved help determine which tests are most likely to be beneficial. Once the results of the testing are returned, we can determine what the best approach to treat the allergy is. If elimination of the cause is not practical, then desensitization is recommended. The solutions used for desensitization are prepared based upon the results of the RAST test. These solutions contain very small concentrations of the offending substances. The desensitization process consists of a series of timed injections. The material injected is a dilute solution of the offending antigen. Each subsequent injection contains slightly more of the antigen. Initially the injections are given two days apart. As the concentration increases, the time between injections is increased, until at the maximum concentration used, the injections are given once per month.
The principle behind desensitization is that certain antibodies (called IgG antibodies) are produced by normal animals, whereas an undesirable type of antibody (called IgE antibodies) are produced by animals that suffer from allergies. The IgE antibodies trigger the allergic reaction when they come in contact with the substance the animal is allergic to. The desensitization process increases the production of the beneficial IgG which is then able to tie up the offending antigen before it binds to IgE and creates the allergic reaction.
In practice, this desensitization results in dramatic reduction of the symptoms of allergy. Many of the pets we have desensitized have gone from being animals that are constantly chewing at themselves, having balding, smelly, irritated skin to being animals that have healthy skin and hair coats with only occasional scratching. They become happier pets, and are much more pleasant to have around. The additional benefit to desensitization is not having to give medication to your pet constantly. This reduces the risk of side effects from the medications, and reduces the trouble you have in having to give medication, baths, etc. to your pet.
What is the next step?
If your pet is having signs suggestive of allergic skin disease, contact us and we can set up an appointment to evaluate your pet and let you know if it is a good candidate for desensitization.
We are available for appointments Monday through Saturday from 9:00 AM to 12:00 noon, and 3:00 PM to 6:00 PM. The receptionist can make an appointment when you call anytime from 9:00 AM until 6:00 PM Monday through Saturday.
Robert L. Linville, DVM
All Creatures Veterinary Hospital
509 Benicia Road, Vallejo, CA 94590