What Are Allergies, and How Do They Affect Dogs?

One of the most common conditions affecting dogs is allergy. In the allergic state, the dog's immune system "overreacts" to foreign substances (allergens or antigens) to which it is exposed. These overreactions are manifested in three ways. The most common is itching of the skin, either localized (one area) or generalized (all over the dog). Another manifestation involves the respiratory system and may result in coughing, sneezing, and/or wheezing. Sometimes, there may be an associated nasal or ocular (eye) discharge. The third manifestation involves the digestive system, resulting in vomiting or diarrhea.

Aren't There Several Types of Allergies?

There are five known types of allergies in the dog: contact, flea, food, bacterial, and inhalant. Each of these has some common expressions in dogs, and each has some unique features.

What Is Inhalant Allergy?

The most common type of allergy is the inhalant type, also known as atopy [AT-ta-pee]. Dogs may be allergic to all of the same inhaled allergens that affect humans. These include tree pollens (cedar, ash, oak, etc.), grass pollens (especially Bermuda), weed pollens (ragweed, etc.), molds, mildew, and the house dust mite. Many of these allergies occur seasonally, such as ragweed, cedar, and grass pollens. However, others are with us all the time, such as molds, mildew, and house dust mites. About 3/4 of atopic dogs first develop signs from spring to fall.

Dogs with atopy may be genetically predisposed to the condition, and certain breeds, such as Schnauzers, Irish Setters, Boston Terriers, Scottish Terriers, West Highland White Terriers, Cairn Terriers and Wire-Haired Terriers, are more commonly affected than other breeds. Female dogs are more likely to be affected than males. Atopy usually first occurs at 1-3 years of age.

What Is Causing My Dog's Allergy?

That is not a question that can be answered easily. The itching produced by ragweed allergy is the same as that produced by oak pollen allergy. In other words, an individual animal or person can be allergic to many different things with the end result (itching) being the same. In some cases, allergy testing can make specific determinations, and sometimes an educated guess can be accurate if the itching corresponds with the blooming season of certain plants. However, it is not always necessary to know the specific allergen for treatment to be successful.

How Is Inhalant Allergy Treated?

Treatment depends largely on the length of the dog's allergy season and involves five approaches:

1. Treatment with natural holistic therapies are often an effective means of controlling atopy. Omega fatty acids ("fish oils"), gamma linoleic [lin-oh-LEE-ic] acid, vitamins A, E, and Zn in conjunction with natural anti-inflammatories such as quercetin [KWER-set-tin] and bioflavinoids frequently can control symptoms.



2. Anti-inflammatory drugs. Anti-inflammatory therapy will dramatically block the allergic reaction in most cases. Natural antiinflammatories should be tried first in conjunction with a fatty acid supplement. Antihistamines combined with the other therapies are frequently very effective, though they can cause mild temporary sedation. Steroids ("cortisone") can be used as a last resort in combination with appropriate supplements and antihistamines. If steroids are appropriate for your pet, you will be instructed in their proper use. When supplementation, antihistamines and steroids are combined, most allergic dogs are significantly improved. This is a non-specific approach which does not treat the allergy, only the result of the allergic state (itching).



3. Shampoo therapy. Many dogs are helped considerably by frequent bathing with a hypoallergenic shampoo. It has been demonstrated that some allergens may be absorbed through the skin. Frequent bathing is thought to reduce the amount of antigen exposure through this route. In addition to removing surface antigen, bathing alone will provide some temporary relief from itching and may allow the use of a lower dose of steroids. Some of the hypoallergenic shampoos incorporate fatty acids; these may be absorbed through the skin and offer a localized anti-inflammatory action. The role of the fatty acids in allergy treatment is an area of active research interest in veterinary medicine.



4. Antibiotics. Dogs that damage their skin by licking, chewing,and scratching are quite susceptible to bacterial infections in the skin. If this occurs, antibiotics should be given until the infection is controlled. The skin infection itself can be quite irritating and cause a dog to itch even more.



5. Hyposensitization. The fifth major form of allergy treatment is hyposensitization with specific antigen injections (or "allergy shots"). Once testing identifies the specific allergens, very small amounts of the antigen are injected weekly. The purpose of this therapy is to reprogram the body's immune system. It is hoped that as time passes, the immune system will become less reactive to the problem-causing allergens. If hyposensitization appears to help the dog, injections will continue for several years. For most dogs, a realistic goal is for the itching to be significantly reduced in severity; in some dogs, itching may completely resolve. This therapeutic approach is recommended for the middle-aged or older dog that has year round itching caused by inhalant allergy Although hyposensitization is the ideal way to treat inhalant allergy, it does have some drawbacks and may not be the best choice in certain circumstances and for these reasons:
   
   
   1. Cost. This is the most expensive form of treatment.
   
   
   
   2. Age of Patient. Because many dogs develop additional allergies as they get older, young dogs may need to be retested 1-3 years later.
   
   
   
   3. Success Rate. About 50 percentof dogs will have an excellent response, about 25 percent get partial to good response, and the remaining 25 percent get little or no response. The same statistics are true for people undergoing hyposensitization.
   
   
   
   4. Food Allergies. Although tests for food allergy are available, the reliability of these tests is so low that it is not recommended at this time. A food trial remains the best diagnostic test for food allergy.
   
   
   
   5. Time of Response. The time until apparent response may be 2-5 months, or longer.
   
   
   
   6. Interference of Steroids. Dogs must not receive oral steroids for two weeks or injectable steroids for six weeks prior to testing; these drugs will interfere with the test result

What Is Meant by the Term 'Flea Allergy'?

In spite of common belief, a normal dog experiences only minor skin irritation in response to flea bites. Even in the presence of dozens of fleas, there will be very little itching. On the other hand, the flea allergic dog has a severe, itch-producing reaction to flea bites. This occurs because the dog develops an allergic response to the flea's saliva. When the dog is bitten, flea saliva is deposited in the skin. Just one bite causes intense itching.

What Does This Reaction Do to the Dog?

The dog's response to the intense itching is to chew, lick, or scratch. This causes hair loss and can lead to open sores or scabs on the skin, allowing a secondary bacterial infection to begin. The area most commonly involved is over the rump (just in front of the tail). This is probably because fleas find this part of the dog more desirable. Many flea allergic dogs also chew or lick the hair off of their legs.

What is the Proper Treatment?

The most important treatment for flea allergy is to get the pet away from all fleas. Therefore, strict flea control is the backbone of successful treatment. The most effective and safest form of flea control is proper daily use of a flea comb. This fine toothed comb will catch any critters crawling on your pet and stimulate the skin to produce natural oils at the same time. Unfortunately, complete flea control is not always possible for pets that live outdoors in warm and humid climates, where a new population of fleas can hatch out every 14-21 days. Some pets can be hyposensitized to the adverse effects of flea bites. Flea saliva extract (flea antigen) is injected into the pet in tiny amounts over a prolonged period of time. This is an attempt to reprogram the pet's immune system so it no longer over-reacts to flea bites. If successful, itching no long occurs or is less intense when the pet is bitten. However, this approach is only successful about 50 percent-75 percent of the time.

When strict flea control is not possible, the other therapies previously mentioned can be used to control the itchiness. In addition, some pets develop a secondary bacterial infection in the skin. When this occurs, appropriate antibiotics must be used.

What is Food Allergy?

A food allergy is a condition in which the body's immune system reacts adversely to an ingredient in a food such as the protein source, or a preservative.

What Foods Are Likely to Cause an Allergic Reaction?

Any food or food ingredient can cause an allergy. However, protein, usually from the meat source of the food, is the most likely offender. Proteins commonly found in pet foods are derived from beef, chicken, lamb, and horsemeat.

Pets are not likely to be born with food allergies. More commonly, they develop allergies to food products they have eaten for a long time. The allergy most frequently develops in response to the protein component of the food; for example, beef, pork, chicken, or turkey. Food allergy may produce any of the clinical signs previously discussed, including itching, digestive disorders, and respiratory distress. We recommend testing for food allergy when the clinical signs have been present for several months, when the pet has a poor response to therapy, or when a very young pet itches without other apparent causes of allergy. Testing is done with a special hypoallergenic diet, and bottled water. Because it takes at least 4 weeks for all other food products to get out of the system, the pet must eat the special diet exclusively for 4-8 weeks (or more). If positive response occurs, you will be instructed on how to proceed. If the diet is not fed exclusively, it will not be a meaningful test. We cannot overemphasize this. If any type of table food, treats or vitamins are given, these must be discontinued during the testing period. There may be problems with certain types of chewable heartworm preventative, as well. Your veterinarian will discuss this with you.

Because pets that are being tested for inhalant allergy generally itch year round, a food allergy dietary test can be performed while the inhalant test and antigen preparation are occurring.

Isn't a Lamb-Based Pet Food Supposed to Be Hypoallergenic?

No, although many people think it is. Several years ago there were no pet foods on the commercial market that contained lamb. A manufacturer of prescription pet foods formulated a food from lamb that was suitable for allergy testing, which will be explained below. Because of that situation, lamb-based pet food was considered "hypoallergenic."