Allergies in pets are frustrating to both the pet owner as well as the veterinarian. It is challenging to find the underlying cause, and often once the cause is identified, it is not something that can be removed from the environment so the dog continues to need ongoing allergy treatment. There are three basic categories of allergies in dogs — food allergies, flea bite allergies and environmental allergies.
Food allergies are challenging because it could be any component of the food (even dyes or fillers can be allergens), although the most common allergens are proteins (chicken, beef, lamb, etc.). In order to determine if food is causing the allergy, you must put the dog on a restricted novel protein or hypoallergenic limited ingredient diet for 6-8 weeks.
During this period of time, you are essentially trying to flush all of the potential allergens out of the dog’s system. It is important to choose a food with a protein source that your dog has not been exposed to in the past. I typically choose a rabbit and potato diet because most dogs have not eaten rabbit before. However, venison, salmon, kangaroo, and fish are all diets that are available. It is important when choosing the food that you look closely at the ingredient list to make absolutely sure there are no potential allergens anywhere in the food. Often things such as poultry digest, egg, beef broth, corn, wheat, or milk products can be found far down on the ingredient list and may interfere with the food trial.
During the 6-8 weeks on the special diet, the dog cannot have any other foods, treats, table scraps, chewies, or even flavored medications as any of these could interfere with the results. Even if the dog licks the empty bowl of the other dog’s food (or gets into the cat food), this can interfere with the results and the 6-8 weeks will have to start all over again. For this reason, people with multiple pets often choose to feed all of the dogs in the household the same food to prevent potential contamination.
At the end of the 6-8 weeks, you will feed back the old diet that you were feeding prior to starting the food trial. During this period, if your dog does indeed have a food allergy, you should see all of the symptoms getting worse (i.e. ear infections returning, itching, chewing and redness getting worse, etc.). If things do not get worse when changing back to the old food, then it is not a food allergy.
Keep in mind that the allergy symptoms may or may not get better completely on the food trial. This is not the point of the trial, as often dogs have multiple allergies and an ongoing environmental or flea bite allergy can continue to cause the dog to have symptoms even if the food is controlling one aspect of the dog’s allergy.
Flea bite allergies are very common in areas where there are fleas. The dog develops a hypersensitivity reaction to the flea’s saliva so when even one or two fleas bite the dog, there is an intense allergic response, usually centered on the top of the back and tail. Flea bite allergies are often the cause of hot spots in dogs. The good news is that fleas are much more manageable since the advent of the newer brand name topical flea controls that are available. Any dog that has skin allergies should be placed on a high-quality year-round topical flea control product that is applied every four weeks, whether fleas have been seen on the dog or not, to prevent the possibility of fleas compounding the allergy problem.
Environmental allergies include seasonal pollens from trees, grasses and flowers as well as environmental mold spores and house dust mites. These are by far the most common allergies and also the most frustrating to diagnose and treat. There are allergy tests for dogs available just as there are for people: There is both a blood test that can be performed at your regular veterinarian as well as a skin test, which can only be performed at a veterinary dermatologist specialist. There is controversy as to which test is the “best” for diagnosing allergies.
Once the offending allergens have been identified, allergy specific immunotherapy can be started to begin desensitizing the dog to the allergens. This is done by giving the dog small frequent doses of the allergens to which she is allergic. Often, this initially results in more intense symptoms because the dog gets itchier when exposed to the allergens. But, the goal is that eventually the dog’s body will become used to the allergens and no longer overreact to them, thus significantly reducing the symptoms.
Unfortunately, this process can take up to two years to see a response and 40 percent of dogs do not show any signs of improvement. A large percentage of dogs respond but will continue to need allergy injections for life. As an alternative for those who do not respond to the allergy injections (or for those who cannot afford this process), there are long term allergy controlling medications. These include fish oil, antihistamines, steroids and cyclosporine (Atopica). The fish oil and antihistamines may help a little but are unlikely to control allergies fully in all but a few mildly affected dogs. Steroids work very well for the majority of dogs but carry with them some serious potential side effects especially if used in the long-term.
Cyclosporine is the current recommended long-term medication for the management of allergies but it does not help all dogs and is a relatively expensive medication. Topical medicated shampoos, conditioners and sprays can all help manage the itching to a mild degree and help remove the offending allergens but are unlikely to help dogs with severe cases.
In addition to managing the allergies, secondary bacterial and yeast infections need to be managed with antibiotics and antifungals. If left untreated, these will contribute to the itchiness level of the dog and result in a vicious cycle of itching and infection. Topical medicated antibacterial and antifungal shampoos often help control and treat infections in addition to oral systemic antibiotics. Keep in mind that often dogs require 30 days or more of treatment to clear skin infections and often dogs with allergies have recurrent infections, which can result in resistant bacteria. As a result, dogs with frequent infections that are not responding to medications will need to have a culture and sensitivity performed on their skin to make sure they are taking the correct medications.