When your dog itches, you know it. That relentless licking, scratching, chewing --anything he can do to relieve the itch. He seems obsessed, and he probably is. Whatever you do, don't ignore this problem (as if you could!). Incessant scratching and chewing may indicate food allergy. He'll constantly tear into any place on his body that he can reach with his teeth or claws. You may see ugly hair loss. Until you find the cause, this problem will go from bad to worse.
Yes, persistent skin irritations can also be due to something else, including dry skin, hormonal issues, liver disease, fungal infections, drug reactions, pain, boredom, anxiety, or a combination of any of those! For this reason, if your dog has chronic itching, it's always worth a trip to the vet to rule out some of these potential causes.
But the fact is, 70 percent of canine skin conditions are allergy-related and most of those are due to flea allergy and/or environmental allergens, such as pollen, mold, or dust mites. If the dog has fleas, or if his symptoms have a seasonal component, it's likely that environmental allergies are his primary problem.
But an estimated 10 to 15 percent of the dogs who suffer from allergies are allergic to their food, or at least some ingredient or ingredients within their food. Many owners assume that a dog with a chronically upset stomach has food allergies, but many dogs who have chronic upset tummies may have a food intolerance; if there is no hypersensitive immune response, it's not an allergy. (That said, one can use an elimination diet to help determine whether the dog is intolerant of certain foods, too.)
The primary symptom of food allergies, just as with inhaled or contact allergies, is itching. Dogs with food allergies might also show gastrointestinal signs (vomiting and/or diarrhea), or secondary infections, such as chronic otitis (ear infections), but they might not; non-seasonal (year-round) itching might be their only symptom.
A DIAGNOSTIC DIET
Puppies aren't usually born with food allergies. These hypersensitive immune responses tend to build up over time, usually appearing between the ages of 1 and 3 (but they can appear late in life, especially if the dog has been on the exact same diet for years and years). The most common food allergens in dogs are protein sources--especially beef, dairy products, wheat, chicken, egg, and soy but the cause may also be a carbohydrate, a preservative, a dye, or anything else in the food.
While there are skin and blood tests that can be performed for allergies, they're expensive and have only a 60 percent accuracy, frequently returning both false positives and false negatives. No wonder many veterinarians consider them useless! Although all you're going to hurt by trying them is your wallet, a far better solution is an "elimination diet."
Better described as a "restricted diet," this limited-fare menu will help you both identify the foods that cause an allergic (hypersensitive) reaction in your dog, as well as find foods that can be fed to him without causing an allergic response.
The first step in a food-elimination trial is to think hard about all the types of food you have fed to your dog, and then gather the ingredient lists for all commercial foods the dog has received, or foods you have included in his home-prepared diet. Write down (or list in a spreadsheet) all of the ingredients in the foods your dog has eaten. While it may be difficult to recall (or impossible, in the case of dogs who were adopted as adults) every food a dog has eaten in his lifetime, all of the ingredients in the diets that the dog has received most recently should be included on the list.
You now have a working list of the ingredients you will avoid when selecting foods for the dog's elimination diet.
The goal for the first stage of the trial is to find ingredients that the dog has never received, in order to find some to which he is not allergic. You will then start him on a diet of these "novel" ingredients, in hopes that his itching reduces and then stops, indicating he is no longer eating something to which he is allergic, and that he is not allergic to any of the novel ingredients.
If his itching and other symptoms of allergy stop, you can begin adding other ingredients back into his diet, one at a time. If the itching recurs, the most recently added ingredient is then put onto your dog's list of forbidden foods.
Ideally, an elimination diet initially consists of just one protein source and one carbohydrate source, neither of which appears on the list of foods your dog has previously eaten.
"I recommend a limited-antigen diet: one protein, one carbohydrate," says Eileen Fatcheric, DVM, co-owner of the Fairmount Animal Hospital in Fairmount, New York. "The foods should be 'novel,' meaning the dog has not eaten them before."
In order to ensure the food is new (novel) for your dog, your veterinarian may recommend some seemingly crazy cuisine. Ingredients often recommended for elimination diets include:
Chickpeas (also a good protein source)
Keep in mind that this initial, "one novel protein and one novel carb" diet is being used in hopes that you have eliminated whatever your dog has been reacting to in his diet, so that he stops itching, his skin clears, and any other allergic symptoms he has cease. Once he is totally a symptomatic--and this may takes weeks--you can add one ingredient to his diet for a few weeks. If he starts itching, that ingredient gets added to the "forbidden" list, and you retreat to feeding the diet that didn't make him itch, wait until all is calm again, and then try adding yet another ingredient.
The ingredients you choose to use for this initial trial should be new to your dog, but readily available to you and affordable. Some of the more unique proteins may be more available in frozen, dehydrated, or canned form than fresh.
Decades ago, beef was the most common animal protein used in commercial dog foods, and so when a dog appeared to have a food allergy, most veterinarians would recommend a lamb and rice food. These ingredients were rarely seen in commercial foods at the time and, therefore, were novel to most dogs. The combination was even dubbed "hypoallergenic"--a misnomer for any dog who is allergic to lamb or rice! Of course, when food-allergic dogs improved on these foods, they became popular; soon, even owners whose dogs didn't have allergies tried them, and more companies began offering foods that contained lamb and rice. The upshot is that within a relatively short time, both lamb and rice lost that all-important "novel" characteristic for many dogs.
The same phenomenon is making it even more difficult for dog owners to find foods that contain ingredients that are novel for their dogs. The popularity of grain-free foods, and their inclusion of potatoes, sweet potatoes, peas, and chickpeas (as replacement carbohydrate sources for grains) means that many dogs have been fed these formerly rare (in dog foods) carbs, eliminating those ingredients from the pool of potential "base" ingredients for the allergic dog's preliminary restricted diet.
Other owners may have fed novel proteins to their dogs in foods that appealed to them for reasons other than food allergies--just to provide the dog with variety, for example.
We suggest that owners avoid feeding foods that contain uncommon proteins to their dogs, so they are available for use in the dog's diet if he should develop food allergies later.
COMMERCIAL FOODS FOR AN ELIMINATION TRIAL?
Today, a visit to any specialty pet-supply store will reveal that any number of companies offer "complete and balanced" foods that contain uncommon proteins such as rabbit, duck, venison, bison, and even kangaroo. Further, many of them are formulated to contain only one type of animal protein--what the makers often call "limited-ingredient" formulas. Those products seem ideal for feeding a food-allergic dog, right? Well, it depends. A commercial food is most likely to work in an elimination diet if it contains just one novel (to your dog) protein and one novel (to your dog) carb. However, if it contains (for example) one novel ingredient (say, rabbit) and chicken --which is the most common animal protein in commercial dog food today --it probably won't work for use in an elimination diet. You have to look past the "headline" ingredients to see whether a food might also contain ingredients your dog has consumed many times; it doesn't matter if a food is called "Brand X Bison and Barley Dog Food" if it also contains beef and rice.
There is also the matter of the potential for cross-contamination at the pet-food manufacturing facility. A dog who is highly allergic to chicken, for example, may react to a food that contains no chicken, but was made on manufacturing equipment that was inadequately cleaned after running a batch of food that contained chicken.
Also, even if it's a single-protein, single-carb "limited ingredient" commercial diet, any "complete and balanced" food will necessarily contain more ingredients than a home-prepared diet that contains only the protein and carb sources. While it's quite rare that the dog's allergy is to a preservative or herb or fiber source in the food, the fewer ingredients that are used in the trial diet, the more certain you can be about what is or is not causing the dog's symptoms.
Another option is to prepare your dog's elimination diet yourself--a course of action that has its own benefits and pitfalls. While it provides you with the ultimate method of ensuring that your dog's diet contains only those ingredients that prove to be safe for your dog, it may take some trial and error to figure out appropriate portion sizes and the best ratio of meat to carbohydrate for your dog. Also, you may be limited as to how long you can keep your dog on the diet, as it isn't likely to be nutritionally balanced.
It can also be expensive. When dog-food manufacturers use something like kangaroo or rabbit in their diets, they have the benefit of buying those novel proteins in bulk, for much lower prices than you are likely to pay. That's why it can be a great boon if you've never fed your dog a diet that contains a common animal protein, that is, when your dog's "novel" protein is something that's easy to find and affordable, like fish or beef.
SERVING THE NEW FOOD
The switch to the elimination diet should take place over the course of a few days. Change your dog's food gradually, substituting increasing amounts of the new food for equal amounts of the old food until the dog is eating only the new food. If you see any signs of gastric distress (vomiting, diarrhea, constipation, which may indicate your dog is allergic to one of the ingredients you have chosen) or if your dog refuses to eat the new food, you'll need to choose different ingredients.
The length of time that you feed the initial diet (of just one protein and one carb), and how long you should wait before introducing a new ingredient, will depend on how your dog's allergies are expressed. Dogs whose primary allergy symptoms include diarrhea, vomiting, and gas will respond (for better or worse) relatively quickly after dietary changes are made.
However, if the dog's primary symptom is itching, it can take a lot longer for the problem to subside after the "trigger" food is removed from his diet. It may also take longer for him to start itching again when a problematic ingredient is added back into the diet.
"For food-allergic dogs whose symptoms are gastrointestinal, you only have to do the 'diet trial' for two weeks," Dr. Fatcheric says, adding that it could take as much as 8 to 12 weeks for skin problems to completely clear.
If there is absolutely no change in the dog's symptoms--no reduction in itching or GI problems--you may want to change both the protein source and the carb source and start a new elimination trial.
If a second trial, with all-new ingredients, produces no reduction in the dog's symptoms, it's very likely that the dog's diet is not what he's allergic to; he most likely is allergic to something else in his environment.
In contrast, if your dog's symptoms reduce immediately and disappear quickly, you will know that there was something in his most recent diet (before the elimination diet) to which he was allergic.
Few owners are willing to take a further step to confirm the link between their dogs' old diet and the dogs' allergy symptoms--a "challenge" phase--but many veterinarians feel this step is necessary. To definitively establish the link between the dog's former diet (or even the single ingredient suspected of being the allergy culprit in the old food), some vets suggest reintroducing the old diet (or the suspect ingredient); if the dog begins to break out in itching or GI distress, the allergen for that dog is decisively confirmed. Quickly return to the diet that your dog did well on, with no allergy symptoms.
Some owners stop there--and who can blame them? It's a pain to employ such scrupulous supervision over your dog's diet. If you feel confident that the trial and challenge have identified the ingredient that is problematic for your dog, you can start looking for (or formulating) a new, complete and balanced diet that is free of that ingredient.
However, it can be incredibly useful to continue for a few more weeks, to challenge your dog with a few more ingredients (one at a time), in hopes of finding more ingredients that are safe for him to consume. Feed him the trial diet until his allergy symptoms are gone again, and then add one ingredient that you would like to use in his diet in the future. If you are able to add it and he doesn't react with signs of allergy within two to three weeks, you can put that ingredient on his "safe" list for now. Once you have challenged his system with a few proteins and carbs without an allergic response, you should have enough ingredients on his "safe" list to enable you to buy or build a complete and balanced diet containing those ingredients (and none of the ones that he's proven to be allergic to).
If you're lucky, you may be able to find a commercial diet that contains only the ingredients on your dog's safe list and none of the ones that trigger an allergic reaction in your dog. But if you can't find such a diet, or want to continue to prepare your dog's diet at home, Dr. Fatcheric recommends that you "work with a veterinary nutritionist to make sure your diet is balanced and complete." Another option is to consult with a company like JustFoodForDogs, which will formulate a diet based on your dog's special needs. (See "Better Choices for Home-Prepared and Special Needs Recipes," December 2013.)
TIPS TO ENSURE CLEAR RESULTS
Make sure your dog consumes only the "trial" food--even for treats. For training treats, use dried bits of the animal protein you are using in the trial. (See "How to Make High Quality Dehydrated Dog Treats" in the May 2012 issue of WDJ.)
Be sure to check any medications your dog may be on, such as a monthly heartworm preventative, to make sure they have no flavorings. If they do or you're not sure, ask your veterinarian for an unflavored alternative. It is critical that you are vigilant about your dog's diet during this time.
If you have several pets, you'll need to oversee dinner time to ensure your dog doesn't eat someone else's meal. Or put all the dogs in the household on the same diet for the trial period. With an elimination diet, your dog can't even lick the cat's bowl clean or gobble down something he finds outside. You'll need to watch everything he does. This is another time when it's valuable for your dog to be happy and habituated in a crate for the periods when you can't supervise him directly.
"I myself would have a hard time being completely compliant for two to three months. No treats (of foods that aren't part of the diet). No nothing. Be careful in homes with toddlers who drop food on the floor. And watch for well-meaning neighbors or in-laws slipping a treat," Dr. Fatcheric says.
A food-elimination trial can be a valuable tool in determining the cause of your dog's discomfort. But it does take commitment, vigilance, and a little extra cash. It's well worth the effort, though, if you do it correctly.
If you stick with the restricted-diet regimen, you should see a reduction in itching by 50 percent or more at the end of the trial. If not, you haven't eliminated the cause. That means you either need to try another combination, consisting of a new protein and new carbohydrate, or determine that dietary hypersensitivity is not the issue. That's why it's so important to involve your veterinarian right from the start.
If the results do prove a dietary cause, you will have been given the key to an itch-free, happy, comfortable dog. You can then either choose a commercial food that contains only those ingredients you used during the elimination trial or consult a veterinary nutritionist to construct a diet that will work for your dog. It's important that the dog's diet for the long-term is complete and balanced.
"Diet trials are hard. But the people with food-allergic dogs who successfully complete them potentially have a comfortable, itch-free pet without expensive and potentially harmful medications. It's worth it, if you can tough it out," Dr. Fatcheric says.
SUSPECT YOUR ITCHY DOG HAS A FOOD ALLERGY?
If you suspect your dog has a food allergy, follow these steps:
* See your veterinarian to rule out other possible causes.
* Save your money if someone recommends allergy tests. They're unreliable.
* Ask your veterinarian to help you construct an elimination diet.
* Choose a carbohydrate source and a protein source that you are comfortable feeding, that your dog will readily and comfortably consume, and that you can afford for weeks at a time. (For instance, fresh ground buffalo may be available from your local Whole Foods, but feeding that as the daily protein source for your 80-pound Labrador may not fit into your budget.)
* Check all your dog's medicines for flavorings and get substitutes, if necessary.
* Stop all supplements during the trial.
* Take photos of all chewed, bare, or irritated spots on your dog's body at the start of the trial, so you have something to compare with as the trial goes on.
* Report any changes in behavior or gastrointestinal upsets to your veterinarian immediately.
* Be vigilant. Watch your dog 24/7 and ensure that he cannot gain access to a food, bone, treat, or chew he is not supposed to eat.
* Keep a journal of your dog's activities. If he has an outbreak of itching, you may be able to use this to determine whether he could have managed to eat something that wasn't on the diet during his outing.
* Once the trial is finished, choose a diet (home-prepared or commercial) that is limited to the ingredients you know your dog can safely consume. If you choose a homemade diet, consult a veterinary nutritionist to ensure the nutrients meet or exceed recommended levels.
COMMERCIAL FOODS FOR ALLERGIC DOGS
Owners who don't feel capable of or willing to carry out a rigorous trial may prefer to try a commercial dog food that has been processed in such a way as to render the proteins hypoallergenic, or one designed specifically for use in an elimination diet. Chances are good that your veterinarian carries at least one of these types of food. Some are limited-ingredient diets, available over the counter; others are prescription diets. All cost around 30 percent more than even the best nonprescription dog foods.
Diets that are described as "low-antigen" are simply limited-ingredient products. These usually contain a single animal protein source and a single carbohydrate source --but they may also contain a lot of other ingredients, any of which your dog could be allergic to. If, after studying your own list of foods and ingredients your dog has eaten while displaying signs of allergy, you are fairly certain that you have identified an ingredient or ingredients common to all of those foods, you may be able to find and successfully use a limited-ingredient diet that does not contain the suspected ingredients.
"Certainly, if your dog stops itching on a diet containing whitefish and sweet potato, you can just heave a sigh of relief and feed that," Dr. Fatcheric says. Keep in mind, however, that dogs who display an allergy to one food ingredient are prone to developing allergies to other ingredients over time. In other words, the whitefish and potato diet may be a blessing to your dog now, but he may eventually become allergic to whitefish and then you will need to start over with a search for a new "novel" food.
Products made with hydrolyzed protein are a completely different solution. Hill's Prescription Diet offers perhaps the best-known of these diets, z/d Ultra Canine. "This is a chicken-based diet, but the chicken protein is molecularly hydrolyzed into smaller amino-acid sequences, which the immune system does not recognize as foreign. Therefore, it won't trigger an allergic reaction," Dr. Fatcheric explains. In the dry version of this product, "starch" is first on the ingredient list, with hydrolyzed chicken liver second, and hydrolyzed chicken fourth; in the canned version, hydrolyzed chicken liver is second only to water on the ingredient list.
Purina Veterinary Diets offers two hydrolyzed diets: HA HypoAllergenic Canine Formula, a vegetarian food made with hydrolyzed soy protein (second to starch on the ingredient list), and HA Chicken Flavor, which also contains hydrolyzed soy protein as the second ingredient (starch is first), but adds hydrolyzed chicken liver and hydrolyzed chicken in the eighth and ninth positions on the ingredient list.
Royal Canin makes six dry foods and two wet foods that contain hydrolyzed soy proteins, as well as an "anallergenic" dry food that is made with "hydrolyzed poultry byproducts aggregate"--which turns out to be made from poultry feathers.
Be aware that the ingredients used in these foods look awful compared to products that meet our selection criteria (see "A Dry Discussion," WDJ February 2015, for more information about identifying a top-quality food). They aren't intended for any but the most intractable, severe cases of canine allergy. For dogs who are hypersensitive to a number of ingredients, they may be the only solution that works well, or works at all. This is one of those rare cases when there are very good reasons to feed a diet containing what we would otherwise consider low-quality ingredients.
TRIALS ARE WORTH THE EFFORT
Allergies can literally cause a dog to tear his hair out, setting acute moist dermatitis ("hot spots") into motion and triggering fits of paw-licking and head-shaking (caused by allergy-induced ear inflammation and infection). When this happens, many owners head to their veterinarians and beg for corticosteroids, antibiotics, pain-relievers, you name it; if it relieves the dog's agony, they want it.
All of those medicines can help a dog who is in acute distress from an allergy attack. But drugs that are prescribed to address the fallout from the symptoms of allergy (scratching and chewing) shouldn't be considered as long-term therapies for any but the most severely allergic dogs. It makes much more sense to try to identify the substances to which the dog is allergic, and then manage the dog's exposure to those substances, than to continue giving him the food that causes so many problems and then treating those problems.
Most people who are allergic to shellfish avoid eating shellfish; few who have suffered swelling, hives, and itching after eating shellfish continue to eat the food and dose themselves with steroids in order to survive the aftereffects! So why do so many people take that approach with their dogs? We have two guesses: We suspect few veterinarians attempt to explain food-elimination trials to their clients, much less encourage owners to try one, because of the weeks of commitment and attention required. And we'd guess that many owners just want the problem treated right then, and when the dog's itching stops overnight with a steroid, they put it out of their minds, as if the problem was solved.
Cynthia Foley is an experienced dog agility competitor. Also a lifelong horsewoman, she served as editor of Horse Journal from its inception in 1994 to 2014.