Dermatology For Animals Blog
The Science and Art of Desensitization (Part 2)
In the past the only way to desensitize a patient was to give the allergen by injection. Now we also have the option of sublingual which is drops under the tongue. Once allergy test results are obtained, these results should always be critically analyzed to insure that the results are consistent with the patients ’itch history. This determination should include historical information regarding what seasons of the year are better or worse. If you have an allergic dog, cat or horse, we always want the client to pay close attention to these details since it can make a difference on our allergen selection. If allergy testing reveals positive reactions only to seasonal pollens in a patient which is pruritic year-round, then something is being missed! There is a saying in medicine that goes “treat the patient, not the lab results”. This certainly applies to desensitization and the selection of allergen but this is where knowledge of the regional allergens is necessary. For the outdoor working dog that is pruritic only in the summer and fall, then positive reactions to grasses and weeds should be present, and they need to be emphasized or prioritized when formulating the extract. For the indoor Chihuahua which sleeps under the covers at night and who is itchy year round, then indoor allergens such as dander, mold spores, house dust and house mites need a higher priority in the extract recipe.
A number of our patients will have significantly strong skin test reactions to over twenty different positive allergens and some will have over 50 significantly positive reactions. In such cases we will often utilize two different vials of allergen to more fully incorporate all the allergens into the immunotherapy program. Another reason to utilize two different vials of allergens is when significant reactions to mold spores occur.
The volume, concentration, and frequency of the allergen injections are additional variables which will affect the success of the immunotherapy program. At Dermatology for Animals we have utilized a “rush protocol” in over 6,000 patients over 25 years. With this schedule, patients receive beneficial levels of allergens within two weeks. We find patients respond more quickly to this program, which can be important for the suffering patient. Yet each patient will respond differently to immunotherapy so there is no “set in stone” protocol. Determining the most effective volume and frequency of injections requires close observations by the owners and the ability of the clinician to make proper adjustments of the protocol. If you have a patient on a desensitization program, we always like to know about any consistent patterns. For example if a patient is receiving an injection every two weeks, and the owner can tell by the 10th day their pet is becoming itchy, that is an example where a smaller amount of allergen given a little more often could give a better response. Finding the minimum effective volume with the maximum duration of effect is our goal when administering immunotherapy.
Occasionally during the course of immunotherapy, owners will observe a flare of pruritus after exposure to certain allergens such as a walk in the park, or a trip to the mountains. Such observations by the owner can be helpful in “fine tuning” the extract contents. For these patients we will make slight or moderate adjustments in the contents of the extract to specifically address the cause of the flare. For example, when an owner reports the patient flares after going outside and walking on the lawn, increasing the grass content in the extract of that particular grass would be indicated.
For many allergic patients, immunotherapy is one of the more safe, cost effective and medically effective options for managing their disease. In general it is easy for most owners to administer. It is an excellent choice in large and or young patients where the long term lower maintenance costs are best realized. It is also an excellent choice for the non-seasonal patient where treatment with corticosteroids or cyclosporin on a long-term basis would have medical or financial drawbacks. Consequently it is not as good a choice for the geriatric patient, or patient with short-term seasonal disease. Immunotherapy does not lend itself to starting and stopping (using as needed) unlike the other medical options.
Written by: Thomas P. Lewis II, DVM, DACVD