Any dog owner whose pet suffers from allergic dermatitis is all too familiar with the constant scratching and itching this condition presents. Understanding the underlying cause for the disease is the first step in finding relief for your dog. There are three main causes of allergic dermatitis: flea allergy dermatitis, atopic dermatitis, and food allergy dermatitis. Additionally, some dogs can have more than one type of allergy.
Clinical signs of allergic dermatitis include pruritus (itching), rubbing, licking, scratching, and chewing. The scratching can be so intense that it causes alopecia (hair loss), reddening of affected skin, and hot spots. A real concern is that dogs suffering with these allergies are prone to secondary bacteria and yeast infections that can result from the damage inflicted by these reactive behaviors.
Atopic Dermatitis (Atopy)
Atopy is a hypersensitivity reaction to inhaled allergens in the environment. Common allergens include pollens, dust mites, and mold spores. Antihistamines, glucocorticoid steroids, and medicated baths are often used to help alleviate the symptoms of atopy. In order to diagnose atopy in canines, veterinary staff use a technique called intradermal skin testing. Allergy shots are then formulated to help desensitize the dog to the allergens that the dog reacted to. The onset of atopy occurs between one and three years of age in most cases, but can occur as early as six months or as late as seven years of age. The areas of skin most commonly affected are the face, areas around the eyes, ears, feet, axillary region (underarm), and groin. However, itching can be generalized throughout the skin. Atopy can be seasonal or non-seasonal depending on the allergen.
Food Allergy
Food allergies are a hypersensitivity reaction to a substance in food. Some of the more common foods that dogs are allergic to can include beef, dairy products, wheat, chicken, chicken eggs, lamb, and soy. Food allergies can occur in dogs ranging from four months to around fourteen years of age, but approximately one third of these dogs will have the onset of food allergies within their first year of life. Skin areas affected by food allergies are practically identical as those caused by atopic dermatitis, making the diagnosis between the causes difficult.
To make this determination, a strict dietary elimination trial must be performed. These diets should consist of a single source of protein (such as duck) and single source of carbohydrate (such as potatoes). It is a requirement that the dog has not been exposed to these food choices previously. There are prescription diets that meet these requirements, such as novel protein or hydrolyzed protein dog foods. If feeding a home cooked diet, work with a veterinary nutritionist to make sure the diet is properly balanced.
During the diet trial, the dog must AVOID the following:
- Flavored medications and vitamin supplements
- Treats
- Table scraps - keep your dog out of the kitchen, especially with young children that may drop food
- Medication in food
- Food intended for other household animals
- Flavored chew toys
The trial diet is fed exclusively for two to three months before reintroduction to the previous diet. If there is an allergic reaction to the reintroduced food within 14 days, then the dog has a food allergy and should return to eating the trial diet. Once the food allergy reaction dissipates again, individual ingredients can be introduced, one at a time, for a period of two weeks each. This will likely determine the specific food substance that causes the reaction.
Flea Allergy Dermatitis
Flea allergy dermatitis (FAD) is a reaction to an antigen in flea saliva. FAD is very common in dogs. Although canines of any age can develop FAD, it usually affects younger patients. Individual dogs react differently to flea bites, and the reaction is worse if the dog has another skin disease as well. Symptoms of FAD include itching the tail base, thighs, and rear third of the dog’s back.
Since flea allergy dermatitis is a reaction to flea saliva, the treatment is preventing flea bites, decreasing the duration fleas are able to feed, and decreasing the number of fleas present on the dog. This is best done by eliminating exposure to fleas. There are many flea control products available in both topical and oral formulations. It is important to treat all animals in the household when dealing with a flea infestation along with treating the inside (home) and outside (yard) environment. Vehicles that pets commonly ride in should be treated as well.
Canine skin allergies create a frustrating problem for dog owners, because what often begins as a seemingly simple condition can evolve into a confusing, and usually painful situation. By properly diagnosing, and subsequently addressing, the root cause of the allergic dermatitis, the daily comfort of your companion can be greatly improved.
Dr. Catherine Gamber received her Doctor of Veterinary Medicine and Bachelor of Science in Biomedical Science from Texas
A&M University. Before moving to the Pacific Northwest she practiced general veterinary medicine in Dallas, Texas.
A&M University. Before moving to the Pacific Northwest she practiced general veterinary medicine in Dallas, Texas.
Her special interests in veterinary medicine include internal medicine, dermatology, and soft tissue surgery. She is passionate about providing the highest quality of care for her dog and cat patients, and has a particular fondness for pot-bellied pigs.
When she isn’t practicing veterinary medicine, she enjoys spending time outdoors running, hiking, and kayaking. Her own pets include a brown tabby cat named Amber and a pot-bellied pig named Eleanor Pigby.
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