Management of canine allergies 8 elements of treatment

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Management of canine allergies 8 elements of treatment

Postby malernee » Sun Nov 16, 2003 6:12 am

<<Proceedings 16th Annual ACVIM Forum, San Diego, CA, 1998, pages 455-457

Leonard D. Jonas DVM, MS, Dipl.ACVIM
Denver, CO

Management of canine allergies varies with the individual dog. Seasonal allergies lasting < 4 months account for 50-60% of the cases and can be managed with antipruritics, and treatment of ectoparasites, pyoderma, Malassezia, and/or seborrhea if present. Non seasonal, long term allergies require an integrated allergy management program. Even with this approach 60-65% of dogs with chronic allergies will require some corticosteroids. The article discusses the 8 elements of the integrated allergy management program:

1. Client Counseling. Take time to make sure the owners understand that these dogs are not cured but rather most need lifetime management; that it takes time and patience to develop an effective program for each individual dog; that there will be flare-ups and secondary problems; and that they will be responsible for medicating, bathing, and observing their pets regularly in an effort to keep them comfortable.

2. Diagnostics. These include skin scrapings, blood tests for metabolic and endocrine disorders, food allergy trials, and inhalant allergy testing.
Food allergy testing. Food allergy testing is done only in dogs with non seasonal chronic allergies. For owners that will make a homemade diet, potatoes (boiled, baked, or microwaved) are recommended as the carbohydrate. Rice is used only if it has not been used in the dog's previous diets. The protein source used is either beans, venison, duck or rabbit. One cup protein is mixed with 4 cups of the carbohydrate and 1 cup of this mix fed per 8-10 lbs. BW. No other foods or treats are fed during the trial. Potatoes can be given as treats. If a commercial hypoallergenic diet is used the label should be examined carefully to be sure that the dog has not been previously exposed to any of the ingredients. It may be necessary to continue the food trial for up to 9 weeks although owners should look for signs of improvement as early as 2-3 weeks. Dr. Jonas feels it is ok to use corticosteroids during the food trial but tapers them ASAP so it can be determined if the food trial is working. ELISA or RAST blood tests are not accurate in diagnosing food allergies.
Intradermal testing is still considered to be the gold standard for diagnosing inhalant allergies by most dermatologist but in vitro testing is advancing rapidly. Identification of the specific inhalant allergens is needed to develop specific immunotherapy and allergen avoidance measures.

3. Medical Antipruritic therapy
a.) Antihistamines. Antihistamines alone are effective in only about 10% of allergic dogs but the efficacy can be significantly increased with the addition of fatty acids and corticosteroids. The newer second generation antihistamines are generally not more effective than older products but may cause less drowsiness and generally cost more. To determine the most effective antihistamine in an allergic dog, sequential 10-14 day trials of 5-6 different antihistamines are recommended. Antihistamines used include:

First Generation Antihistamines:
- Chlorpheniramine at 4-8 mg/dog with a maximum of 0.5 mg/kg BID to TID
- Diphenhydramine (Benadryl) at 2-4 mg/kg BID-TID
- Clemastine (Tavist) at 0.05-0.1 mg/kg BID
- Hydroxyzine (Atrax) at 0.5-2 mg/kg TID
- Trimeprazine (Temaril) at 0.5 mg/kg BID
- Doxepin (Sinequan) at 0.5-2 mg/kg
- Amitryptyline (Elavil) at 2.0 mg/kg BID

Second Generation Antihistamines:
- Fexofenadine (Allegra) at 0.25 mg/kg SID
- Astemizole (Hismanal) at 1.0 mg/kg SID
- Loratadine (Claritin) at 10 mg/dog SID

b.)n-6 and n-3 Fatty Acids. Clinical trials have reported a favorable response in 20-30% and up to 45% of patients treated with fatty acids. The optimum ratio of n-3 to n-6 fatty acids is unknown but higher levels of n-3 fatty acids appear to produce more of the less inflammatory leukotrienes and thus more effectively reduce the inflammatory response. To be effective, fatty acids may be needed in doses 4-10 times higher than the levels found in current commercial products.

c.) Topical cleansing and topical antipruritics. Secondary seborrhea oleosa is often present in atopic dogs. Giving regular baths as needed can reduce the pruritus and make the dog feel and smell better. Antiseborrheic shampoos can be used if indicated. Finishing with an emollient shampoo or rinse is suggested to avoid drying of the skin. Although shampoos containing antipruritics, antihistamines, steroids, oatmeal, etc can significantly reduce pruritus the effect does not usually last long. Even using cool water by itself is felt to be beneficial and can help reduce percutaneous absorption of allergens.

d.) Corticosteroids. Most dogs will need some steroids. Hopefully they will only be needed sporadically but if needed they can be given eod or every third day.

4. Allergy Immunotherapy. If an allergen that makes sense can be identified with allergy testing, immunotherapy is recommended as it can safely reduce the symptoms in 75% of the cases. However it can take up to 12 months of therapy before improvement is seen clinically.

5. Antibiotics. Secondary bacterial pyoderma is seen in about 90% of atopic dogs and contributes to the pruritus. Antibiotics should be given for 3-4 weeks. Some antibiotics commonly used include:
- Cephalexin at 10-20 mg/kg BID or TID
- Cephadroxil at 25 mg/kg BID
- Lincomycin at 15-25 mg/kg BID
- Erythromycin at 10-222 mg/kg BID-TID
- Trimethoprim sulfa at 10-15 mg/kg BID
- Amoxicillin/clavulonic acid at 12.5-25 mg/kg BID
- Fluoroquinolones at 5-10 mg/kg BID

Tetracyclines, penicillin, and ampicillin should be avoided because of the ability of Staphylococci to quickly develop resistance to these antibiotics.

6. Antifungals including ketoconazole at 10 mg/kg daily for 14 days and antifungal shampoos like chlorhexidine are recommended for the treatment of Malassezia.

7. Allergen avoidance. Remove offending allergens from the dog's direct environment. Limiting the time the dog spends outdoors in the morning is also suggested since pollens tend to be at their highest levels at that time.

8. Air filtration to reduce indoor pollens and dust.
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