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Wednesday, November 3, 2010

Itchy Dogs

It's been a rough autumn for dogs with allergies. I am spending most of my recent days, it seems, treating uncomfortable itchy canine patients. My clients are frustrated, my patients are miserable, and my staff, well, they're learning a lot about skin disease!

While airborne allergens cause people sinus and airway irritation, in dogs they almost always cause dermatitis. There are many many causes of skin disease in dogs (demodectic mange, sarcoptic mange, ringworm, hypothyroidism, etc...), but well over half the cases we see have an allergic component. There are three major categories of allergic skin disease in dogs: flea allergies, food allergies, and atopic dermatitis (environmental allergies). It can be difficult to sort out which type of allergy a dog may have, especially since it's not uncommon for a dog to suffer from more than one of the three major types. Add in the fact that allergic skin disease is often complicated by secondary bacterial and/or yeast infections, and the diagnosis can be challenging!

Treatment of atopic dermatitis first involves identifying and addressing all other skin issues (bacterial or yeast infections, dry or greasy skin, fleas, thyroid conditions, etc...) Once these have been identified and treated, the allergic condition will be easier to manage. In a dramatic oversimplification, I will describe four medical approaches to control atopic dermatitis:
Glucocorticoids ("steroids")-This group of medications typically works really well for atopic dogs. They are also pretty inexpensive. Unfortunately, they can cause all kinds of long- and short-term side-effects. They are considered the least-safe drugs for long-term therapy. Dogs on long-term or repeated doses of glucocorticoids should be monitored with blood and urine tests. (Side note: Clients love these drugs because they're cheap and work great. They tend to get testy when we recommend other, safer options, or require labwork to refill the glucocorticoids!)
Antihistamines -These drugs do not work as well as glucocorticoids, but can be effective in mild cases or patients whose severe symptoms have been controlled with glucocorticoids. Sometimes we have to try several different kinds of antihistamines to find the one that works best for a given dog.
Atopica -This is the new "wonder drug" for atopic dermatitis. It is reported to work nearly as well as glucocorticoids while being much safer for long-term use. It is a much more expensive drug, and must be given year-round. Therefore, I only use it for patients whose symptoms occur over half the year and do not respond well to antihistamines.
Hyposensitization Therapy -This is similar to what is done in people with severe allergies. The dog is tested to find out what she's allergic to, then small amounts of those substances are given to her by injection at regular intervals so she will become tolerant of the allerge ns. This is an expensive, and time-consuming process. I have had mixed results in my patients who have had this done. It is certainly the most "natural" approach to treating atopic dermatitis.

The most important thing that I have learned about atopic dermatitis over the years, and the thing I always emphasize to new veterinarians and veterinary students, is that no two atopic dogs are the same and the dog owner must always be forwarned that it will take some time and patience to discover what will work best for their dog.