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 localised (one area) or generalised (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 diarrhoea. The specific response that occurs is related to the type of allergy present.
Does that mean that there are several types of allergies?
There are at least five known types of allergies in the dog: contact, flea, food, bacterial, and inhalant. Each of these has some common features and also there are some unique features.
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 and this is of a long lasting nature.
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?
Other link: Flea control
The most important treatment for flea allergy is to get the dog away from all fleas. Therefore, strict flea control is mandatory and this involves ensuring the dog is flea-free and also removing fleas from the environment. There are many products available for flea control, and many work in entirely different manners. In some cases, multiple products may be needed. Some are used on the dog and some on the dog's environment. Unfortunately, flea control is sometimes difficult, particularly with dogs living outdoors in summertime when the weather is warm and humid, where a new population of fleas can hatch out every 14-21 days. Good control of fleas on the dog and in the environment is important. Flea Control
When strict flea control is not possible, corticosteroids (or "cortisone" or "steroids") can be used to block the allergic reaction and give relief. This is often a necessary part of dealing with a flea allergy. Some dogs respond best to long-acting injections and others to oral medication. Dogs are more resistant to the side-effects of steroids than humans, but significant side-effects can occur. For this reason, the goal is to administer the smallest amount of steroid needed to keep the dog comfortable. Some dogs develop a secondary bacterial infection in the skin. When this occurs, appropriate antibiotics must be used and steroid therapy reduced even further.
ATOPY Back to top
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 localised (one area) or generalised (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 diarrhoea.
What is contact allergy or atopy?
The most common type of allergy is the contact type, also known as atopy. Dogs may be allergic to all of the same allergens that affect humans. These include tree pollens (cedar, ash, oak, etc.), grass and weed pollens, moulds, mildew, and the house dust mite. Many of these allergies occur seasonally, such as the grass pollens. However, others are with us all the time, such as moulds, mildew, and house dust mites.
What happens when a dog comes into contact with something to which it is allergic?
When humans inhale allergens, we express the allergy as respiratory problems. These include coughing, sneezing, a runny nose, and watery eyes. The dog's reaction, however, usually produces severe, generalised itching. It will chew, lick, or scratch almost any area of the body, including the feet. Chewing and scratching produce hair loss and inflamed areas of the skin. Saliva will stain light coloured hair, so dogs that lick excessively will have orange or reddish brown hair. This is often seen on the feet. Although most people think that itching is related to fleas, the most common cause of itching in the dog is inhalant allergy.
What is causing my dog's allergy?
That is not a question that can be answered easily. The itching produced by grass pollen is the same as that produced by oak pollen allergy. In other words, an individual animal 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.
What is meant by "seasonal allergy" and "year round allergy"?
As the names imply, some dogs only have allergic reactions during specific periods of the year. Others will itch year round. A year round allergy occurs for two reasons. First, the allergen is present year round. This is the case for indoor dogs that are allergic to house dust mites, also known as "house dust". Second, the dog is allergic to so many things that at least one of those allergens is present at all times.
My dog seemed to have a seasonal allergy for several years, and now it seems year round. Is that possible?
Not only is that possible, it is almost expected. As the dog ages, it usually becomes allergic to more and more things. After several years of acquiring new allergies, it reaches the point that it is constantly exposed to something to which it is allergic.
How is atopy treated?
1. Anti-inflammatory drugs. Anti-inflammatory therapy will dramatically block the allergic reaction in most cases. Corticosteroids ("cortisone") may be given orally or by injection, depending on the circumstances. If steroids are appropriate for your dog, you will be instructed in their proper use. Antihistamines can be of value in treating the allergic dog when they are combined with steroids. In some dogs, antihistamines can significantly decrease the amount of steroid needed to provide relief. Fatty acid supplementation can also be implemented with steroids and antihistamines. When the three of them 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).
2. 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 localised anti-inflammatory action. The role of the fatty acids in allergy treatment is an area of active research interest in veterinary medicine.
3. Hyposensitisation. The third major form of allergy treatment is hyposensitisation with specific antigen injections. 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 hyposensitisation 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. Generally, steroids are only used on a brief and intermittent basis. This therapeutic approach is recommended for the middle-aged or older dog that has year round itching caused by inhalant allergy.
4. Omega 3 and 6 oils in the diet can play a role to help the skin barrier.
5. Specific diets are available that can help in soothing and protecting the skin to reduce the itch. They also contain omega 3 and 6 oils.
6. 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.
Although hyposensitisation 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:
(a) Cost: This is the most expensive form of treatment.
(b) Age of Patient: Because many dogs develop additional allergies as they get older, young dogs may need to be retested 1-3 years later.
(c) Success Rate: About 60% of dogs will have an excellent response, about 20% get partial to good response, and the remaining 20% get little or no response. The same statistics are true for people undergoing hyposensitisation.
(d) 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.
(e) Time of Response: The time until apparent response may be 2-5 months, or longer.
(f) Interference of steroids: Dogs must not receive oral steroids for 2 weeks or injectable steroids for 6 weeks prior to testing; these drugs will interfere with the test results.
FOOD ALLERGY Back to top
What is food allergy?
A food allergy is a condition in which the body's immune system reacts adversely to a food or an ingredient in a food.
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 dog foods are derived from beef, chicken, lamb, and horsemeat.
Isn't a lamb-based dog food supposed to be hypoallergenic?
No, although many people think it is. Several years ago there were no dog foods on the commercial market that contained lamb. A manufacturer of prescription dog foods formulated a food from lamb that was suitable for allergy testing, which will be explained below. Because of that situation, lamb-based dog food was considered "hypoallergenic".
Dogs 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 dog has a poor response to steroids, or when a very young dog itches without other apparent causes of allergy. Testing is done with a special hypoallergenic diet. Because it takes at least 4 weeks for all other food products to get out of the system, the dog 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 types of table food, treats or vitamins are given, these must be discontinued during the testing period.