GreatDanes Online

Shadow · Site Admin Joined: 15 Nov 2007 Posts: 26

Dogs also get allergies, just as we do. Like us, dogs can have respiratory or digestive problems caused by allergies, but most likely they will itch. Allergic reactions are rarely fatal for dogs, though they are a persistent nuisance and, for some especially sensitive dogs, a source of ongoing misery.

A severely allergic dog may itch constantly, damaging its skin and coat with continual scratching, biting and rubbing. The skin damage may result in secondary bacterial and yeast infections. An allergic dog may also have chronic and occasionally severe respiratory or digestive problems. Or, in the worst-case scenario, succumb to anaphylactic shock. However, with proper diagnosis and treatment, most dogs can live in relative comfort.

Allergies are the physical expression of the immune system’s over-reaction to substances, called “allergens.” Allergens are not normally irritants and will not bother a normal individual. Allergens can range from pollens and molds to common food items. Flea bite dermatitis is the most common canine allergy; the allergen involved is the saliva of fleas.

Allergies are often discussed in the media, heightening our awareness and sometimes prompting us to call something an “allergy” when it really is not. Diagnosis of canine allergies should be made by a veterinarian; not through the owner’s assumptions.

Even though allergies generally don’t develop until a dog is at least six months old, allergen exposure usually takes place before four months of age. An allergy does not develop unless there has been prior exposure, which allowed the immune system to recognize the allergen and “decide” that it needed to be attacked if encountered again. This attack upon subsequent exposure is what causes the allergic reaction. Exposure can occur through breathing or eating the allergen or getting it on the skin.

Environmental factors that contribute to allergies include not only exposure to allergens, but parasite load and the administration of vaccines. If a dog has parasites, the immune system will react to their presence. The greater the parasitic load, the greater the stress on the dog’s immune system. This can lead to severe allergic reactions if the dog is also exposed to allergens. Fleas are the most problematic parasites where allergies are concerned, but heartworm and intestinal parasites can also set the dog up for allergy attacks.

Both killed and modified live vaccines are potentially allergenic, though for very different reasons. Killed vaccines contain chemicals called adjuvants that enhance the efficacy of the vaccine without exposing the dog to the pathogen. The adjuvants can cause an allergic reaction. In the modified live vaccines, the toxins produced by the pathogen are what cause the reaction. One should keep in mind that in both cases, the vaccines are not the cause of the allergy, but the trigger. A dog must be genetically predisposed to allergies for the reaction to take place.

ATOPIC DERMATITIS
Atopic dermatitis, a hypersensitivity reaction of the skin, is the second most common form of allergic reaction in dogs. When a dog is exposed to an allergen, usually by inhaling it, the immune system begins producing Immunoglobulin E (IgE), a special type of cell designed to target the allergen. The IgE activates mast cells that release several different substances including histamine, a chemical that causes itching, inflammation and swelling. Most mast cells are found around the feet, ears and anus so allergic reactions of the skin appear more commonly in these areas. If the skin within the ear is affected, the dog may also develop secondary ear infections. Dogs may also experience allergic respiratory problems, digestive problems and eye irritation, but these are much less frequent than the skin reactions.

FOOD ALLERGIES
Food allergies are a common cause of itching and account for about 15 percent of all allergic skin disease in dogs. (see section on food additives)

In contrast to inhalant allergies, which cause dogs to itch during certain seasons, food allergies can cause itching all year round. Typically, pets don't respond to antihistamines and other medications for skin allergies. Of course, some pets have food allergies along with flea-bite sensitivity or inhalant allergies. These pets usually have severe symptoms if they are not treated.

The most common clinical sign of a food allergy is intense itching, which can last all year and doesn't respond to medication, even steroids. These dogs will constantly lick their feet. Unlike humans, dogs itch when they have allergies.

Sometimes skin lesions will occur, but they vary in severity and location. Dogs with food allergies often get ear infections.

Dogs with food allergies are allergic to certain proteins or carbohydrates in pet foods. They can be allergic to more than one food substance. The best way to diagnose a food allergy is using a food elimination diet and should only be done through the guidance of a veterinarian.

This diet consists of only one single source of protein and carbohydrate to which the pet has not been previously exposed. The diet must be followed exclusively for a minimum of 13 weeks.

Dogs with a food allergy will show improved signs as early as four weeks with resolution of all signs by three months. The key here is that the only things the pet can eat are these single sources of protein and carbohydrate. One piece of chicken will throw everything off.

Once the clinical signs have resolved themselves, introducing the original diet will bring about the allergic reaction usually within 10 days of restarting that diet.

To diagnose which ingredient is the culprit, you restart the elimination diet, and once clinical signs have resolved, start adding in single food ingredients and monitor for allergic reactions.

The most common allergens include beef, chicken, fish, pork, lamb, egg, dairy, corn, wheat, soybeans, rice and potatoes.

The portion of an allergen to which the immune system reacts is called an epitope. The proteins found in wheat have over 50 epitopes, so it is not surprising that allergic dogs often react to wheat-based feeds. Affected dogs tend to vomit within a couple hours of eating and may sometimes have loose stools. Skin reactions are not unusual. These dogs may have difficulty maintaining weight, despite a good appetite. Severely allergic individuals have chronic diarrhea, significant weight loss and poor coat quality. Food allergies often arise after a case of infectious enteritis.

The most severe—and potentially fatal—form of allergic reaction is anaphylactic shock. It can occur after eating something containing an allergen, an injection of drugs or vaccine, or the bite of an insect. Affected dogs will have difficulty breathing. Their gums will be pale due to a drop in blood pressure. Immediate veterinary treatment is necessary. Be sure to read the LINK on Is Your Pets Food Healthy?

FLEA ALLERGY DERMATITIS
Your dog doesn't have to be "loaded" with fleas to develop this condition. In fact, a dog that is hypersensitive to the saliva that a flea puts into their skin when it bites will experience immediate itching and redness from only one bite.

As the dog continues to bite and chew, it causes hair loss, skin abrasions and eventually develops a skin infection. This, in turn, makes the dogs itch even more. A common term for this is called a "hot spot."

If you suspect that your dog has a sensitivity to fleas, the best thing you can do is prevent your pet from getting bitten in the first place. Have your veterinarian design a flea plan for your pet and stick to it year-round. This should include eliminating the fleas from the environment as well as your pet.

All animals in the house must be treated. There are good, cost-effective products like Advantage Interceptor, Sentinel and Frontline that are available from your vet. The key to choosing products for dogs with flea bite hypersensitivity is to choose products that will kill fleas on contact before they have a chance to bite. Depending on the severity of the symptoms, your veterinarian may prescribe steroids, antihistamines, antibiotics, fatty acid supplements and medicated shampoos or topical treatment.

YEAST INFECTIONS
Yeast infections are another common cause of itching in dogs. These pets usually have red itchy skin that has a distinct odor.

There are many predisposing factors that contribute to the development of yeast infections. Pets with folds in their skin, hypothyroidism, compromised immune systems and chronic steroid use may all predispose an animal to developing yeast infections.

Diagnosing yeast infections can be difficult because yeast is a common resident of normal skin in dogs and infection only occurs when there is an increase in population. Excessive scratching, increased moisture and excessive seborrhea can also cause an animal to develop a yeast infection.

Your veterinarian can detect yeast infections using slides and a microscope and sometimes even a skin biopsy.

There are several ways to treat yeast infections including topical and oral medication. Most pets will stop itching within one to two weeks after starting treatment. However, recurrence is common, so your veterinarian should monitor your pet closely.