Allergies

Allergies are caused by an immune system response to the presence of various proteins in the environment. These proteins can be in food, in the air, places where your dog rests, or elsewhere in the dog’s environment. Proteins do not mean just meat! Every living thing contains proteins. That means your dog can develop an allergy to any sort of plant, fungus, pollen, insect or other creature, as well as protein sources in his food. Sources of protein in food are not just meat, but grains and other plants have proteins that your dog can become sensitive to over time. Allergies in dogs can be called simply allergies, atopy, skin allergies, flea bite dermatitis, or food allergies. If you have a dog with allergies, you may have heard one or more of these terms used by your vet.

How do allergies work? Your dog’s body creates immune complexes called immune globulins, in response to proteins in the environment. Immune Globulin E, or IgE for short, is formed by your dog’s immune system when exposed to certain proteins over a period of days or weeks. These IgE molecules bind or attach to the outside of cells called mast cells. This binding is  known as “sensitization” and just means that now your dog’s body is “primed” to act if that protein should ever show up again. 

Some proteins are easy to avoid, and in so doing, make it easy to avoid having allergy symptoms. For instance, humans who have shellfish or macadamia nut allergies can easily avoid these items in their diet, and avoid a reaction. On the other hand, people with grass or peanut allergies often have reactions, because these proteins, or allergens, are very common in the environment, and difficult to avoid.

Symptoms of allergies happen when the allergens enter the body, and then the IgE “captures” them. Once trapped on the cells, the body’s histimines come to the rescue and “attack” the bound allergens, destroying them. It is actually the histimines that cause symptoms. The location of the mast cells is what causes allergy reaction symptoms. Mast cells can occur anywhere in the body, but in humans are more common in the respiratory tract. In dogs, they are more common in the skin and digestive tract. That is why humans usually have respiratory (sneezing, coughing) reactions, while dogs have itchy skin, rashes, and diarrhea when they have allergies.

In a recent study, it was found that a little over 7% of dogs in one veterinary clinic. Of these, 40% had some kind of skin reaction, while another 40% had digestive symptoms. The remaining 20% were pretty evenly divided between respiratory symptoms, and other symptoms, like red, runny eyes. So we see that most dogs with allergies will have skin problems or digestive problems, while a few will have symptoms more like human allergies: itchy, swollen eyes, coughing, sneezing.

Allergy Symptoms

Allergy symptoms can vary, but in dogs are primarily focused on the skin and digestive tracts, where mast cells are most common. Dogs with inhalent allergies (atopy), flea allergies and contact allergies (from lying on bedding, grasses, etc.) will show varying degrees of skin irritation and scratching. This scratching can be very intense. Hair missing from parts of the body is caused by damage from scratching and biting. Skin can become reddened and thickened from both the histimine reaction and from the physical trauma from scratching/biting. Scabs, clear or yellowish secretions from the skin (sometimes bloody) and crustiness of the skin can also occur. Other signs may be more subtle, such as obsessive licking and biting of the feet. Over time, the feet can become brownish colored from the dog's saliva. Some dogs with inhalent allergies will have itchiness and redness around the lips and eyelids, and these dogs will often rub their faces on the furniture or other surfaces to relieve the itching. Dogs with food allergies may also have the same skin problems as other allergic dogs. Sometimes, these skin issues may be more subtle. Digestive symptoms are also common in dogs with food allergies. Vomiting and digestive reflux are common. Diarrhea or soft, poorly formed stools are also a symptom of allergies. Yeast infections of the ears that are hard to clear up or reoccur often, even when the dog has not been swimming, can be a symptom of food allergy.

Diagnosing and Treating Allergies

Often times, diagnosis and treatment of allergies goes hand-in-hand. Getting the dog's symptoms under control and the skin or digestive tract calmed and functioning normally is usually the first priority. Some vets will run allergy tests concurrently with treatment, while others will simply start treatment, and its success is diagnostic in itself. Depending on the severity of the problem, further testing may be ecessary to identify the protein or proteins a dog is most reactive to, so that the owner can remove those protesin fropm the dog's diet or environment as much as is possible.

Allergy tests, such as skin or blood tests, are somewhat diagnostic, but not as useful in dogs as they are in humans. Many times, identifying the allergens that are triggering a dog's allergies is a process of elimination. For environmental allergies, it means removing, one by one, objects or possible allergens in the environment (for instance, eliminating fleas, or not letting the dog lie on grass), until the dog shows improvement. That way, you know exactly what it is the dog was allergic to. Treatment can be as simple as removing that item from the dog's environment, or can be more complicated. For instance, dogs who are allergic to certain pollens cannot easily avoid those pollens because they blow around in the air. In these cases, a veterinary internal specialist or dermatologist can formuulate allergy shots for the dog that will gradually accustom your dog's immune system to that allergen, reducing the severity of the dog's reaction, or eliminating it altogether. Click here to locate a board certified Veterinary Dermatologist near you.

For dogs with food allergy, identifying the protein that causes the problem requires removing all proteins larger than about 3,000 Daltons (how protein molecule size is measured). This is usually done through specially formulated diets that your vet can prescribe. The immune system cannot identify these smaller proteins, and will not react to them when present in the dog's food. The dog will be placed on this diet for varying lengths of time, depending on the severity of the dog's food allergy, and also how quickly the dog responds to the new food. Typically, the dog will be on the low allergen diet for 8-10 weeks, until the dog's immune system has returned to normal.

Once the dog is doing well on the special food, "normal" proteins will start to be added back into the dog's diet one by one, so that the one(s) that the dog reacts to can be identified. Remember, proteins include all plant matter, so the dog should not be switched off the special diet until the process of adding ingredients back into the dog's diet is complete. As with inhalent allergies or skin allergies, a skin or blood test can be somewhat helpful in identifying some of the proteins a dog is allergic to. Each ingredient that is added will be maintained for a few days to weeks to see how the dog reacts. The entire process can be quite lengthy, but very rewarding, as the owner can get a good idea what foods the dog can be fed. The entire process is known as an "elimination" diet, as you are testing, one by one, each protein, and eliminating those that cause a reaction.

It is very important while a dog is on an elimination diet, that ALL sources of protein are controlled. Otherwise, the results of the feeding trial can be hard to interpret. That means all natural-based treats, chew toys, etc. bust be eliminated from the diet (at least temporarily) as well. No pig ears, marrow bones, dog biscuits, etc. (yes, even the vegetarian ones!) Treats and reward foods will need to be added back into the diet and the dog's reaction monitored just as with the dog's main diet.

Living with an Allergic Dog

Once the underlying causes for a dog's allergies have been identified, maintaining that dog can be simple or very complex, depending on what the dog is allergic to. If the allergen is an isolated source (such as cedar bedding, or fleas), it may be easy to control them in the environment. More widespread allergens, such as grass or tree pollens, may mean using allergy shots to reduce the severity of reactions. For dogs with food allergies, a word of caution: it is popular among some dog owners to switch food brands periodically. However, remember that a dog develops allergies to proteins it is exposed to, and the longer or more frequently the dog is exposed to that protein, the more likely it will develop an allergy. This means that the more foods, and the more ingredients a dog that is prone to allergies is exposed to, the more allergens it may develop a reaction to. If a dog with allergies has been exposed to a wide range of protein sources, its owner may have a difficult time finding any ingredient that the dog is not allergic to. It is better to limit the type and number of protein sources (animal and vegetable/grain sources) to a few, so that should the dog develop allergies, you will have a different (what allergists call "novel") protein source readily available. For instance, a dog who has been fed beef-based foods all its life, and develops an allergy to beef can easily be switched to a food that is chicken or lamb based. However, a dog that has been fed beef, and chicken, and lamb, and maybe other meat-based foods on a rotating schedule every few months, may develop allergies to all of these meat sources. Finding a food that does not contain any of these proteins may be very difficult.

Controlling symptoms while the source of the dog's allergies is still being identified is very important. For dogs with skin symptoms, special shampoos, medications such as steroids (to control the itching) and antibiotics (for any secondary skin infections) may be prescribed. It is very important to follow the vet's instructions exactly when giving these medications. Some dogs may be given an Elizabethan collar to wear to prevent them from chewing their tail or feet, or to prevent face rubbing. Some vets wrap the feet to keep the dog from foot chewing. Dogs with ear yeast infections may be given medication to treat the infections. Anti diarrheal or anti vomiting medication may be prescribed for dogs with digestive symptoms. Your dog will be "weaned" off of these medications gradually by your vet, so that any return of symptoms can be noted.

Dogs with allergies may have other underlying conditions as well. If a routine allergy treatment program does not seem to help, your vet may wish to do test to look for these other problems. Dogs with conditions such as hypothyroidism or irritable bowel syndrome are more prone to developing allergies as well. If your dog's case is complex and involves more than one condition, you may wish to consult a Veterinsry Internal Medicine Specialist. An Internist can manage complex allergy cases because they are trained to balance all of a dog's body systems when treating a condition. To locate a board certified Veterinary Internal Medicine Specialist, click here.

Article on food allergies from LSU Vet School