Definition of Allergies
Allergies, also known as hypersensitivities, are acquired overreactions by a dog’s immune system to something that it perceives as being foreign and potentially dangerous, called an “allergen.” Common canine allergens are food ingredients, pollens, grasses, weeds, plants, flea and tick saliva, mites, chemical cleaners, detergents and other household products, plastics, drugs, carpet fibers and cigarette and cigar smoke. Allergies often cause skin problems, ear irritation and gastrointestinal upset. Affected dogs may scratch, lick or bite at irritated skin areas, creating sores that can become infected. The constant head shaking and scratching from “allergic ears” can cause blood-filled blisters, called hematomas, on the bottom of the ear flaps. Dogs with allergies can develop significant behavioral changes because of the inescapable discomfort associated with their condition.
Causes of Canine Allergies
An allergy is an acquired and exaggerated defensive reaction by an animal’s immune system to something that it perceives as being foreign and potentially dangerous. The offensive substance is called an “allergen.” Acquired allergic reactions, also called hypersensitivity reactions, develop over time. The first exposure to the offending allergen stimulates the dog’s immune system to go into a state of readiness. This includes producing antibodies to that specific allergen. Subsequent exposures trigger a full-blown, complex, highly regulated immune response, because the cells of the immune system recognize the allergen and have been primed to find and destroy it.
There are four main categories or causes of allergies in dogs:
Contact allergies are triggered by a dog’s repeated exposure to some irritating substance that comes into direct physical contact with its skin. Common canine contact allergens are chemicals in household cleaners, shampoos, flea collars, fertilizers, insecticides, medications, natural and synthetic clothing or furniture fibers, plastics, seasonal pollens, trees, bushes, grasses, weeds, flowers and other plant products. Contact allergies usually are most noticeable to owners on areas where their dog’s skin is not well-protected by hair, like the nose, feet, groin, belly and between the toes.
Injection Allergies, of which the most common are caused by flea bites. In a nutshell, dogs with this condition become hypersensitive to the saliva of fleas, ticks or other blood-sucking external parasites. Flea bite allergies trigger an immune reaction to the fleas’ saliva, which causes intense irritation and itchiness and can increase the risk of secondary bacterial infections and localized hair loss at the bite site.
Inhalant Allergies Many dogs develop allergies to environmental substances that they inhale. Common culprits include cigarette and cigar smoke, fireplace smoke, seasonal pollen from weeds, trees, grasses and other plants, and many other things. Inhalant allergies are second only to flea bite allergies in terms of frequency in dogs. The severe skin itchiness and irritation associated with inhalant and some contact allergies is called “atopy.” Many contact and inhalant allergies, in both dogs and people, are casually referred to as “hay fever.”
Food allergies can develop from hypersensitivity reactions to almost anything in a dog’s diet. Common canine food allergens include beef, dairy products, corn, wheat, eggs, chicken, lamb and soy.
Preventing Allergies in Dogs
The best way to prevent allergic reactions in dogs is to keep them from coming into contact with, eating, inhaling or otherwise being exposed to whatever allergen is causing their hypersensitivity. For example, flea bite allergies are best prevented by removing the allergen – fleas – from the dog’s body and immediate living environment. There are a number of good commercial products to help owners prevent or resolve flea infestations. Owners of dogs with flea allergies should consult with their veterinarian about the best approach to control the problem. To prevent the symptoms of hay fever, owners should keep their dogs away from whatever seasonal allergen is causing the problem, to the extent that they can. Food allergies can be prevented once the culprit in the dog’s diet is identified. This can be done through a strict ingredient elimination diet supervised by a knowledgeable veterinarian. Many of the newer kibbles contain novel protein sources, such as venison, bison, duck and fish, which can be extremely helpful for dogs that are allergic to more common protein sources, like chicken, beef or lamb.
Special Notes
Canine allergies can be difficult, but not impossible, to diagnose and manage.
Initial Evaluation
Anyone who has seen a dog continually scratching and chewing on itself probably has seen a dog with allergies. Whether caused by airborne inhalants, fleas or ingredients in food, allergies cause discomfort that can range from simple irritation to severe secondary bacterial infections. The definitive cause of allergies is difficult, but not impossible, to diagnose. A veterinarian’s initial evaluation will include taking a thorough history from the dog’s owner about the dog’s health and symptoms, including when they started, whether they are sporadic or always present and whether they are progressively getting worse or staying about the same. The vet will also conduct a physical examination, paying particular attention to carefully assessing the dog’s skin and ears.
Diagnostic Procedures
The most common cause of allergic reactions in dogs is also the most common cause of allergic reactions in people: seasonal hypersensitivity to something in the air or environment, like pollen, a particular weed or some crop being harvested in the area. Seasonal allergies usually can be diagnosed based on when the symptoms show up and the extent of the dog’s access and exposure to the environmental allergen. Flea bite allergies are also extremely common in dogs and are usually fairly easily diagnosed based on physical evidence of flea bites and flea infestation.
If an allergic reaction lasts for quite a while or occurs randomly rather than seasonally, it probably is caused by something other than a seasonal allergen. Advanced tests are available to help identify specific allergens. A veterinary dermatologist can discuss these tests with the dog’s owner in greater detail. Allergy testing is expensive, somewhat invasive and can be a bit painful. A less invasive way to diagnose the cause of a dog’s allergies is to systematically remove suspected allergens from its environment or diet and then slowly reintroduce them one at a time, evaluating whether the problem subsides or recurs. Fabrics, carpet fibers, dust mites, cleansers and detergents, household items made of rubber or plastic and even excessive dust can induce allergic reactions, so they should be considered in these cases.
If food allergies are suspected (and they are quite common in domestic dogs), the dog’s veterinarian probably will recommend what is known as an “elimination diet.” This means putting the dog on a bland diet with very few ingredients – typically just rice and chicken for starters. The owner will observe her dog for any adverse signs of reacting to those simple ingredients and, if none are present, will then gradually add other foods to the dog’s diet, one at a time. The owner must keep a close watch on how her dog reacts to each new ingredient to determine which food items he is allergic to. Once those are identified, the dog’s diet can be restructured.
It is extremely helpful to determine the source of an allergic reaction before a treatment protocol is established. Simply treating the affected area may help relieve the dog’s symptoms temporarily. However, the underlying cause of the allergic reaction probably will remain in the dog’s diet or environment and undoubtedly will cause additional uncomfortable symptoms in the future, if it is not identified and removed or managed.
Effects of Allergies on Dogs – From the Dog’s Point of View
Dogs, like people, commonly develop allergies. Canine allergies usually cause dermatological (skin) problems, ear irritation and/or gastrointestinal upset. Allergies can be extremely detrimental to a dog’s health and to its quality of life. Continual scratching, licking and biting at irritated areas of skin often leads to physical sores, which can become infected. When the ears are affected, the constant head shaking and scratching can cause hematomas to develop, especially on the tips of the ear flaps. Hematomas are basically blood-filled blisters. If allergic reactions are particularly severe and prolonged, the dog may develop significant behavioral changes as well, as a result of its continual and inescapable discomfort.
Symptoms of Canine Allergies – What the Owner Sees
The visible signs of allergies mimic those of many other conditions. Dogs with allergies usually develop skin problems, ear problems or digestive/gastrointestinal upset. Owners of affected animals may notice one or more of the following symptoms:
Skin Irritation
- Itchiness; scratching; biting at skin
- Redness, rash; common in the groin and flank areas, on the paws, between the toes, behind the front legs (in the armpit/axial area), under the neck and on the chin
- Sneezing
- Bumps and white raised pustules; pimples
- Lethargy; weakness; general malaise
- Restlessness
- Red, weeping eyes
In an effort to relieve skin irritation, affected dogs may exhibit:
- Frequent and relentless scratching at affected areas
- Licking or chewing at affected areas
- Rolling on the floor or ground
- Moist sores called hot spots; prone to becoming infected
Ear Irritation
Dogs with allergies frequently develop infections or other irritation on their external ears and in their ear canals. Symptoms may include:
- Frequent and relentless scratching at the ears
- Head shaking; often vigorous and persistent
- Thinning of the hair in and around the ears
- Waxy build-up in the ears
- Abnormal yeast-like smell coming from the ears
Gastrointestinal Irritation
Dogs with allergies – especially food allergies - often have gastrointestinal disturbances in addition to skin and ear irritation. The gastrointestinal tract includes the stomach and the small and large intestines. Common signs associated with allergies to ingredients in food include:
- Burping
- Vomiting
- Diarrhea
- Flatulence
- Loss of appetite
- Weight loss
- Lethargy
- Weakness
- Depression
- Loss of interest in normal activities
- Hives
- Enlarged lymph nodes
Food allergies can continue undiagnosed for years. Many owners mistakenly believe that their dogs’ symptoms are just caused by a sensitive stomach.
Dogs at Increased Risk
There are some recognized genetic components to canine allergies - especially to contact and inhalant allergies. Predisposed breeds include Shar-Peis, Cairn Terriers, West Highland White Terriers, Scottish Terriers, Lhasa Apsos, Shih-Tzus, Wire-Haired Fox Terriers, Dalmatians, Irish Setters, English Setters, Golden Retrievers, Labrador Retrievers and Miniature Schnauzers. Most dogs don’t develop acquired allergies until they reach adulthood.
Goals of Treating Canine Allergies
When an owner suspects that her dog may be suffering from some sort of allergy, she should take pet to a veterinarian for a comprehensive assessment. It may be necessary to consult with a specialized veterinary dermatologist to identify the problem and bring it under control. Often, the underlying causes of a dog’s allergies will never be figured out. The overriding goals of treating canine allergies are to control the immune system’s hypersensitivity response in order to alleviate itchiness, pain and discomfort and restore the dog’s healthy, comfortable quality of life. “Curing” allergies in dogs is rarely attempted or accomplished, although it is possible in some cases using advanced treatment techniques.
Treatment Options
Allergies in domestic dogs are usually treatable, or at least manageable. The treatment protocols vary depending on the severity of a particular dog’s condition. For example, if a dog’s symptoms are caused by an immune reaction to flea saliva, the owner has many available options to help eradicate the parasites from the dog’s body and from its immediate environment. If the dog is allergic to airborne allergens, such as cigarette smoke, the owner should remove those substances from the home or yard. If particular plants or pollens seem to be the culprits, the owner might consider walking the dog in a different direction to prevent it from coming into contact with those seasonal allergens.
A number of topical treatments are available to soothe a dog’s irritated skin, reduce inflammation and calm itchiness, no matter what the cause. These include shampoos, lotions, gels, creams, rinses and other treatments. Oral antihistamines, such as Benadryl, can be used to reduce the effects of seasonal allergies. Prescription anti-inflammatory drugs, including corticosteroids, can help relieve itching and provide comfort to dogs suffering from allergies. Advanced, long-term treatments are also available to help desensitize and acclimate a dog’s immune system to the allergens that trigger its allergic reactions. These options are something that owners need to discuss with their local veterinarian or a specialized veterinary dermatologist. Of course, a veterinarian is the best one to advise owners about the appropriate treatment for dogs with allergies.
Dogs with food allergies, which are quite common, need to have their diets modified and closely managed. The first step is to identify the ingredients that cause the allergic reaction. The dog’s veterinarian probably will recommend what is known as an elimination diet. This involves putting the dog on a bland diet with very few ingredients – typically just cooked rice and chicken for starters. The owner will observe her dog for any adverse signs of reacting to those simple ingredients and, if none are present, will then gradually add other foods to the dog’s diet, one at a time. She must keep a close watch on how her dog reacts to each new ingredient to determine which food items he is or isn’t allergic to. Once the allergens are identified, the dog’s diet can be restructured. Owners of dogs with food allergies can use homemade diets or take advantage of the many specialized dog foods that now are commercially available in most areas, including a number of kibbles with unusual protein sources such as salmon, venison, bison or duck.
Prognosis
Dogs with allergies typically have a very good prognosis, once the allergen is identified and appropriate treatment begins. The most difficult part of this process is identifying the allergen. Once the allergen is pinpointed, there are many positive steps that can be taken to reduce the dog’s allergic reactions and restore its quality of life.
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