Allergies
Allergies are a frustrating chronic disease process that pets and humans suffer with. An allergic reaction is a damaging immune response, by the body, to a substance (pollen,dust,food) to which the body has become hypersensitive. This reaction causes cells in the body to release histamine. Histamine is a body chemical which creates inflammation. Inflammation (redness, heat, pain, and swelling) creates the clinical signs that pets suffer from. Each species seems to have a body system sensitive to histamine. In the dog the most common organ systems involved are skin and gastro-intestinal. In humans and cats the systems affected tend to be the respiratory system and skin. Allergies are an inherited disorder which can affect any breed of dog.
Acute allergic reactions are a little different than chronic allergic disease. Acute reactions are characterized by a severe histamine release causing a dramatic event. This type is characterized by hive formation, facial swelling, vomiting and sometimes respiratory compromise (swollen airway). This type is typical in response to a bee sting, and sometimes a vaccine. This type of allergic reaction needs immediate therapy usually in a hospital situation. Most of the time this reaction is treated with injectable steroids and antihistamines. Some animals may even need Intravenous fluid therapy in order to control a drop in systemic blood pressure. If treated appropriately there is no long term damage to the body. If not treated appropriately this can be a life threatening event.
Common types of chronic allergies are Flea allergies, Food allergies, and Inhalant allergies.
Flea Allergies
When a flea bites a dog it injects a small amount of saliva into the skin. Dogs can be allergic to this saliva and hyper-react. The hypersensitivity to the saliva causes an intense itch response which makes dogs scratch. The hypersensitivity reaction last for several days causing the dog to continue to scratch. Clinical signs (scratching) are concentrated around flea season. The key to treating this reaction is to prevent fleas from coming in contact with the dog. There are many excellent products on the market to protect dogs during flea season. If a dog has a flea allergy reaction they may need antihistamines or short-term steroid therapy to control the itch.
Food allergies
When a dog eats, food is processed in the gastrointestinal system and nutrients (proteins, fats and carbohydrates) enter into the blood stream. Dogs can have a hypersensitivity reaction to constituents in the diet. The hypersensitivity creates an inflammatory reaction and the dogs may suffer from vomiting, diarrhea and/or itchy skin. The clinical signs of food allergies are year round and relentless since the dog is coming in contact with the allergen all of the time. Food allergies can be very difficult to diagnose. Testing involves food trials which limits constituents in a diet. This is generally done by feeding simple ingredient home cooked diets or using a commercial hypoallergenic diet. Each elimination diet needs to be fed for 6 weeks at a time. It can take months to find the correct diet for a particular food allergy dog.
Inhalant allergies
This hypersensitivity reaction is caused by the inhalation of tiny particles in the air (pollen, dust, dust mites,etc). These are the most common type of allergies and the most frustrating to treat. The clinical signs with this type of reaction tend to be seasonal depending on which inhalant particle a dog is allergic to. For example a dog that is allergic to trees and grasses tend to suffer in the spring and fall where dogs allergic to dust have more clinical signs in the winter when there is less air flow in a house. Diagnosis of inhalant allergies is achieved by either skin testing or blood testing. Typically a regional panel of allergens are tested and there is controversy on which technique gives a more accurate picture of which pollens a dog is allergic too.
Once an dog is diagnosed with allergic disease treatment needs to be instituted in order to control the clinical signs that the pet is suffering from. Dogs that suffer from allergies are typically extremely itchy, may have hair loss (common areas are the axilla, flanks, ventral chest and abdomen and under the tail area). They maybe suffering from secondary skin infection from bacteria or yeast. The secondary infections tend to create scales and crusts or dandruff. common treatments for allergies are as follows:
- Antihistamines: These are drugs used to prevent the release of histamine into the bloodstream. Less histamine release means less inflammation and then less scratching. Some common antihistamines used are Clemestine, Hydroxyzine, Diphenhydramine, loratadine, and cetirizine. These drugs have relatively few side effects mostly causing lethargy.
- Avoidance of allergens: This is relatively easy to do with flea allergy, and food allergy once the food allergen is diagnosed. This is almost impossible with inhalant allergens. Air filters, use of air conditioners in the summer, baseboard heating as opposed to force air heating in the winter, removing carpets will help a little.
- Steroids: This is a group of drugs that have strong anti-inflammatory activity but also have damaging side effects. It is not a good choice for long-term management but some dogs need these drugs for short term relief. The most commonly used steroid is Prednisone either on its own or in combination with an anti-histamine.
- Cyclosporin: This is a strong immuno-suppressant used at low doses to decrease the bodies inflammatory response. This drug is becoming more common as a long term management tool. The side effects are less than steroids but it is more expensive.
- Immunotherapy: This is a vaccine made for allergens that have been identified through allergy testing. A specific serum is made for each dog based on the allergy test results. the serum is actually tiny doses of allergens which are injected into the dog. The serum stimulates the immune system to create antibodies that fight off the allergen. This takes time for the body to make these antibodies so this type of therapy can take a long time to work. Most of the time the pet owners are taught how to give these injections and are given a schedule to follow. The goal in this therapy is to limit the amount of other drugs needed to control the petŐs clinical signs (scratching).
- Fatty Acid Suppliments: There has been a lot of research on the benefits of Omega 3 Fatty acids on the general health of the skin and the immune system. Most studies have shown that these suppliments do help considerably. They are general anti-inflammatory activity and do seem to allow a lower dose of other drugs.
- Antibiotics: There are many different antibiotics that have effect in the skin. The specific drug is usually chosen depending on the type of bacteria infecting the skin. Bacterial skin infections tend to be a secondary invader taking advantage of the unhealthy skin environment in the allergic dog. If pustules and scabs are involved in the dogŐs skin lesions the bacteria needs to be controlled.
- Antifungals: There are a few antifungals used to treat yeast infections effecting the skin. Yeast is also a secondary infection in allergic skin disease. Yeast infections tend to make dogs intensely itchy, and show flakes on the skin. the most commonly used drug in this group is Ketoconazole. All anti-fungals are metabolized by the liver and can cause some elevation of liver function tests.
- Bathing: Giving an allergic dog a bath can be very beneficial. A bath washes the surface bacteria and yeast off of the skin. Some additives in a shampoo can also act to relieve itchiness (ie. colloidal oatmeal). Some yeast infection can actually be completely controlled by bathing. Different shampoos will be used for different skin problems. A veterinarian will make a choice based on all of the factors affecting a particular dogŐs skin problem. When using a medicated shampoo the shampoo needs to be in contact with the skin for 5-10 minutes in order for it to have the greatest benefit.
Allergies can be a very frustrating problem for both the dog and the owner. This is a chronic disease process that can be well managed if all components of the disease are controlled. This is an inherited disorder and many breeds including mixed breeds will be effected. It can take a long time to identify what a dog is allergic to but is worth the testing since advanced technology has allowed us to get better control over the disease. The more control we have over each component of the skin disease the more comfortable the dog and owner. Remember allergies can be controlled but not cured. All allergic dogs will need some sort of maintenance protocol.
<< Back
Dr. Ellen Leonhardt
Animal General
East Norwich
(516) 624-7500
THIS SITE PROVIDES INFORMATION, NOT MEDICAL ADVICE
Information on this web site is provided for informational purposes only and is not intended as a substitute for the advice provided by your veterinarian or any information contained on or in any product label or packaging. You should not use the information on this web site for diagnosing or treating a health problem or disease, or prescribing any medication or other treatment. You should always speak with your veterinarian before giving any medication or nutritional, herbal or homeopathic supplement to your dog, or adopting any treatment for a health problem. For any products or services purchased from this web site, you should read carefully all product packaging and instructions.
|
