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All About Allergies

All About Allergies

By Dr. Andy Hillman


     As many of you know Northwest Florida is an allergy mecca.  With our humidity and temperate climate, we play host to a wide range of allergens from trees, grasses and other vegetation.  On top of these potential triggers, our flea population is very prolific and most dogs with allergies are very sensitive to flea saliva.  Everyday household cleaners and detergents also can be a source for allergic outbreaks.  Food allergies are often overlooked but cause major issues. With all these opportunities, many dogs have one or more of these allergies and it is a constant battle to keep them comfortable.

     When a dog comes into contact with an allergen it stimulates histamine production which leads to inflammation.  Unlike humans that sneeze, cough and have watery eyes, dogs itch when they are exposed to allergens.  The location of the itching can be an indication of what type of allergen they are sensitive to.  As I said, most allergic dogs have what is called flea allergic dermatitis. This condition, which is triggered by flea saliva, causes severe itching in the hind quarters of the affected dog and can lead to hair loss and open sores.  Airborne allergies cause a dog to itch mostly on their feet, face and ears.  This allergy is called atopy and about 10% of dogs are thought to be genetically predisposed to this condition.  Contact allergies are also common and the symptoms are similar to atopy but usually result in itching on the chest, stomach and feet.  The last allergy is food allergies.  When a dog is food allergic the most common signs are diarrhea, vomiting and chronic ear infections.  Unfortunately in most cases dogs have more than one type of allergy, which makes a clear diagnosis problematic.  Treatment for allergies is complicated, time consuming and sometimes expensive.  

     Good parasite control is usually the first step in an allergy treatment plan and now more than ever we have products that make this step easier.  Pet owners and veterinarians have been asking drug companies for complete parasite control for years. Now there are two products that with only one exception are true all in one products.  Trifexis is a pill that combines the flea-killing pill Comfortis and the heartworm and intestinal parasite control of Interceptor.  The two major drawbacks with Trifexis are that it is not effective against ticks and the main side effect is vomiting.  There is also Advantage Multi that is a topical that has Advantage for fleas and a transdermal moxidectin for heartworms and intestinal parasites.  Again, Advantage Multi doesn’t prevent ticks and since the flea control is topical it can be washed off.   In the months ahead I plan to write an entire article about parasite control and the pros and cons to each product on the market.  Keeping an allergic dog flea free goes a long way to keeping it comfortable.

     The most important goal in treating allergies is to make the dog as comfortable as possible.  There are four treatments that have varied success, cost, and side effects.  Antihistamines, allergy testing and desensitization injections, cyclosporines (Atopica) and of course, corticosteroids are the options available for treating allergies.  Sometimes it takes a combination of two or more of these treatments to be effective.

     There are very few allergy treatment plans that do not include antihistamines.  The most common one that I use in my practice is Hydroxyzine, which is the human drug Atarax.  Benadryl (diphenhydramine), Tavist (Clemastine), Clortrimeton (Chlorpheniramine), and Claritin (Loratidine) are some of the other antihistamines that can be used on dogs.  The advantages for using antihistamines are that they are relatively inexpensive and can be immediately effective.  The main side effect of these medications is drowsiness, but they can be used long term without injuring the dog.  The drawbacks are that they have to be given multiple times a day and sometimes they lose their effectiveness once the dog’s system becomes use to them. 

     The only medication that provides a higher level of effectiveness and immediate relief than antihistamines is corticosteroids.  The most well known corticosteroid is prednisone.  I use prednisone in different forms to provide relief to severely allergic animals.  Unfortunately, these drugs have major side effects and must be used judiciously.   Corticosteroids are the strongest anti-inflammatory known to man, but it puts stress on the liver and kidneys that over time can do permanent damage to these organs.  These drugs also suppress the immune system making the dog open to other infections.  The good things about these drugs are the low cost, high effectiveness, and convenience.

     There is a drug made by Novartis called Atopica.  This medication works very much like corticosteroids, but doesn’t have all the same side effects.  Atopica is a modified cyclosporine, which is a drug that has been used in the eyes to help tear production.  There are two major drawbacks to this drug.  Atopica is expensive, especially at first and if the patient is a large dog this treatment may be cost prohibitive.  The other problem is that some dogs will vomit while on this drug.  This complication can be reduced by keeping the medication in the freezer or adding a medication for nausea.  In most cases, this medication is well tolerated and effective.  Atopica is a much safer option than corticosteroids.

     The last option for treating allergies is to send a blood sample to a lab where it is tested against the most common allergens.  Once the allergens are identified a personalized serum can be produced for the dog or, in some cases, the allergen can be removed from the dog’s environment.  Allergy testing and serum is expensive and requires a high level of involvement from the owner.  In the beginning of this treatment, daily injections are required so an owner must either learn to give the injections or be willing to drive to the clinic every day.  The good part of this treatment is that over time it is usually effective and there are not any negative side effects on the dog’s health.

     Food allergies can be the easiest or the hardest to treat.  When a dog has food allergies the most common allergens are wheat, corn, beef and chicken.  Most major dog foods contain one or more of these ingredients.  Even formulas marked lamb, salmon or rice can contain other ingredients, so it is important to read the entire list of ingredients on the label.  The other things to avoid in commercial dog foods are preservatives and artificial coloring.  Remember dogs can’t see color so it is put in pet foods for the owner not the dog.  Now there are several companies that make food specifically with these allergy dogs in mind.  These foods are made with novel proteins and carbohydrates like venison, duck and potatoes.  There are also dog foods that have been treated to remove the proteins that trigger the allergic response in the dog.  If there is a suspicion of food allergies, I will suggest a food trial to diagnose the allergy.  The most important thing to remember is that everything the dog eats must meet the same guidelines as the special diet.  A truly food allergic dog can react to a small treat or piece of table food. 

     Treating allergies is obviously a major part of my practice.  I know that huge advances in treatment have been made and as we keep studying this problem more discoveries will come to light.  Allergy management is a team effort that takes time, effort and money.  With diligence and good communication with a veterinarian a pet owner can keep their allergic dog comfortable and healthy.