Dog Food Allergies Causes and Cures
We talked to Dr. Justin Shmalberg, a DVM and Nom Nom's own veterinary nutritionist, to create this comprehensive guide that covers the following:
Dog Food Allergies vs Dog Food Intolerances
"What most people think of as a dog food allergy is more appropriately called a cutaneous adverse food reaction or CAFR," says Dr. Justin Shmalberg, a DVM and Nom Nom's own veterinary nutritionist. "It basically means there's some association between a food and a certain group of symptoms—usually skin problems or gastrointestinal problems."
In a true dog food allergy, according to Shmalberg, the culprit is often a food protein that triggers an adverse immune response, which then causes cells in the body to release histamines or compounds that lead to itching and many other allergic signs.
A dog food intolerance, on the other hand, doesn't involve an immune response—but the signs of dog food intolerance can look pretty similar to the signs of a food allergy. One example is a lactose intolerance, which happens when a dog's body just doesn't process lactose in milk products well, leading to gastrointestinal problems (often diarrhea).
Both allergies and intolerances fall under that category of CAFRs, or, in more general terms, adverse food reactions. So, how prevalent are adverse food reactions in dogs? One 2017 research review published in BMC Veterinary Research examined just that. The findings suggest that, of dogs seeing vets for any diagnosis, 1 to 2 percent have food intolerances or allergies; among dogs with skin diseases, the number jumps up a bit, to about 6 percent. For dogs with itching and allergies, even more—about one in five—show signs of adverse food reactions.
Still, true allergies, in which the immune system is attacking a food protein, are definitely less common than food intolerances. The takeaway, says Shmalberg, is this: "If your dog is otherwise normal, even if he's scratching a lot, a food allergy is unlikely. That said, diet can certainly play a role in helping to manage skin conditions and diseases, regardless of whether or not your dog has a food allergy." We'll discuss more about how you can tell the difference below.
Most Common Dog Food Allergens
"Meat, dairy, and eggs are often thought to be the most common dog food allergens," says Shmalberg. "Yet generally, it's the protein part of those foods that tend to be problematic, rather than, say, the meat itself." Keep in mind, veggies can contain protein, so they're not automatically safe.
That same review BMC Veterinary Research identified some of the most frequently reported dog food allergens involved in adverse food reactions. Here's a look, from most-reported to least-reported.
Top Dog Food Allergens (source: BMC Veterinary Research)
|Dog Food Allergen||Percentage of Dogs With Reported Reaction|
Shmalberg calls out two important caveats to keep in mind here.
- Newer research is needed.
Many of the studies out there, and those sourced in this review, are older, when dog foods were being made and processed differently than they are today. Allergies tend to change over time along with foods, and as new studies emerge, we may see different allergens rising to the top of the list.
- The more common a food is, the more likely the allergy.
"For an allergy to a food to develop, a dog needs to be exposed to that food," says Shmalberg. "That may explain why the proteins most commonly found in dog food, like beef and chicken, fall higher on the list."
More facts about dog food allergens that are helpful to know:
- Where there's one allergy, there may be more.
It's estimated that more than a third of dogs with one food allergy are allergic to at least one additional food.
- Starches are safer.
Pure carbohydrates, aka starches, are pretty low in or free of protein, which means dogs usually aren't allergic to them. There are exceptions: while potato starch is probably safe, whole potatoes might cause an allergy because they contain proteins. Same goes for higher-protein grains like corn and wheat. But overall, grain allergies are much less common than meat allergies.
- With fats, purity matters.
Pure fats, like fish oil, are free of protein and shouldn't trigger a response. But traces of protein can sneak into oils and fats during processing, and in a highly allergic dog, cause issues.
- Look out for gelatin.
Supplemental oils often come in gelatin capsules, and that gelatin can trigger allergies in some dogs.
- Peanut allergies are rare in dogs.
And if they do occur, they typically aren't of the severity reported in some humans. Good news if your pup is one of the many who love a PB treat!
- No two foods are exactly the same.
There's not a good deal of evidence to suggest that a dog who has a reaction to one food it is going to react to a similar food. That is, a dog allergic to chicken won't necessarily be allergic to turkey.
- Watch for additives.
Chemicals, preservatives, colorants, and flavorants aren't likely to cause a true allergy, but they could trigger an adverse reaction or intolerance symptoms.
- Food labels don't always tell the whole story.
Some non-fresh kibble and canned foods have tested positive for proteins even when they're not listed on the label.
Dog Food Allergy Symptoms
Sneezing. Ear infections. Chronic Diarrhea. Restlessness. Dog food allergy symptoms run the gamut from skin reactions to gastrointestinal troubles to behavioral issues. Below you'll find a full list, broken down by category, to help you identify whether your pup might be suffering from a food allergy or intolerance. Note, it's estimated that about a quarter to a third of dogs with a food allergy also has an environmental allergy, which "has similar and at times indistinguishable, symptoms," says Shmalberg.
Most Common Signs of Food Allergies in Dogs
These are the signs you'll see most often with a food allergy, says Shmalberg, starting with the single most common symptom: itching.
- Itching (aka pruritus)
- Itchy paws
- Hot spots
- Skin rashes
- Scaly and/or oily skin
- Pigmented skin
- Leathery skin texture
- Eye discharge
- Red eyes
- Hair loss
- Ear infections
- Secondary yeast or bacterial infections (aka pyoderma) of the skin or ears
One study ranked the parts of the body most often involved in itching related to food allergies, as follows:
- Ears (involved 80 percent of the time)
- Paws (61 percent)
- Inner thigh/belly (53 percent)
- Eye or front leg area (33 percent).
Gastrointestinal Food Allergy Symptoms in Dogs
According to Shmalberg, only 10 to 30 percent of dogs with confirmed food allergies have gastrointestinal, or GI, symptoms like vomiting or diarrhea. "This is a condition that is much more often linked to skin symptoms," he explains (see above). "Sudden and short-lived GI symptoms are almost never caused by a food allergy. On the other hand, food allergies can contribute to or cause certain chronic symptoms."
- Diarrhea with or without blood and/or mucus in stool
- Straining to pass stool
- Abdominal pain
Rarer Symptoms of Food Allergies in Dogs
These symptoms aren't as common as those above but may occur in some dogs.
- Nasal discharge
- Breathing issues
- Seizures (food allergies could trigger them in predisposed dogs)
- Secondary urinary tract infections (due to overgrowth of skin bacteria)
- Weight loss (in combination with severe diarrhea and/or vomiting)
Dog Behavioral Issues from Food Allergies
The symptoms below are also rarer, and usually secondary to or linked to discomfort from symptoms listed above.
- Frequent scratching of self on furniture, owner's legs, etc.
- Frequent shaking ears or scratching ears
- Biting at paws, rear end, and/or tail
- Withdrawal or reduced interest in playtime
- Anorexia, or disinterest in or refusal of food
Long-Term Effects of Dog Food Allergies
If a food allergy goes untreated, there are some more serious health issues that could develop. These include secondary skin infections, the development of more allergies, worsened symptoms, behavioral changes, and a poor quality of life.
If your dog is constantly itching, it can feel like having a thousand mosquito bites all the time and lead to poor quality of life.
Dog Food Allergy Test and Other Diagnosis Methods
So, how can you tell if your dog is allergic to food? First, it's helpful to know how you might distinguish a food allergy from an environmental one. "Environmental or flea allergies are far more common," explains Shmalberg. If you suspect either of those, consult your vet, who can help identify and treat fleas, or do a combination of blood tests and/or intradermal allergy testing (which involves injections of potential allergens under the skin) to assess environmental allergies.
But if your dog has the following signs, talk to your vet about setting up a dog food allergy test or elimination diet.
Telltale Signs Your Dog May Have a Food Allergy (vs. an Environmental or Flea Allergy):
- If the symptoms occur at a very young age—typically, puppies younger than age 1 don't experience environmental allergies
- If the symptoms aren't tied to a seasonal change or don't change in different parts of the country (e.g. if you travel or move with your dog from a dry climate to a humid one)
- If the reaction doesn't respond to steroids
- If your dog has both skin and gastrointestinal symptoms
Dog Food Elimination Diet
The most reliable way to diagnose a food allergy is to feed your dog something entirely new, and relatively pure, for at least eight weeks. For accurate results, you'll need to feed a non-contaminated simple ingredient diet (it can be commercial or cooked) for the entire trial. Most importantly, says Shmalberg, "the diet should include a single-source animal or vegetable protein and a single source of carbohydrate calories, without other natural flavors (that could have unidentified proteins)—and it must be a food your pet hasn't had in the past. Classic examples include venison and potato, rabbit and pea, and fish and potato." There are newer options out there too, like alligator and coconut.
It's also important you refrain from feeding treats, table scraps, snacks, and flavored medications and supplements of any kind that don't match the specific ingredient combo you're using for the trial. After eight weeks, to truly prove the food allergy, you must then feed the original food—the suspected allergic protein or proteins—again. If there's a reaction or breakout at that point, that's a pretty good indication of an allergy.
"The reality is that most owners don't complete this part, as they don't want their dog to have symptoms again," says Shmalberg. "An owner might just continue to feed the trial food if it seems to be agreeing with the dog." But reintroducing the suspected allergens is really the only way to confirm an allergy. Shmalberg suggests cycling through potential allergens one by one—chicken, beef, egg, dairy—to see what does (and does not) trigger symptoms.
Other Types of Dog Food Allergy Testing
Aside from elimination diets, there are a couple of other test options worth a look.
- Blood tests: Blood tests exist, but they're not very accurate. "There are new food allergy blood tests in development, which appear better than those on the market," says Shmalberg. "That means, for now, a food elimination diet is the best option.
- Patch tests: Patch tests are generally thought to be more accurate than blood tests. Yet, according to Shmalberg, "They're not commonly done but may be offered in a dermatology clinic, where a protein (e.g. beef) is mixed with petroleum jelly and taped on the skin for about two days, then tested a day later. If there's irritation (redness, hives), it's considered a positive test; if not, it's negative.
Genetic Predisposition to Dog Food Allergies
Wondering whether your dog might be predisposed to food allergies or intolerances? Certainly there's some evidence that if a parent has an allergy, their offspring is more likely to inherit it. So in that way, genes do play a role. But what doesn't seem to be a factor is a dog's breed. In fact, science has never confirmed that any one breed is more at risk for food allergies than another. "It can happen in any breed and in any dog," says Shmalberg.He also notes that some breeders and owners may have the view that deviating from the ancestral diet of certain breeds might predispose to allergies. For example, Huskies are accustomed to fish diets in their natural habitat—so could feeding them poultry lead to an allergic reaction?
In short, no. "There is no evidence to support that theory. Most dogs seem pretty adaptable to a range of foods," says Shmalberg. The age or sex of the dog also appears to have no relevance to food allergies or intolerances. Some vets do report that food allergies have been found in dogs less than 1 year old. So even young puppies can be affected (whereas they typically aren't as susceptible to environmental allergies at this age).
Here are the top 10 breeds most frequently Googled along with the term "food allergies" or "dog food allergies":
- Golden Retrievers
- German Shepherds
- Cocker Spaniels
- Shih Tzus
- Westies (aka West Highland White Terriers)
- Yorkies (aka Yorkshire Terriers)
Keep in mind, food allergies can happen in any breed, and, of course, some breeds may be searched more frequently just because they're more popular in general.
Dog Food Allergy Treatment
Dog food allergy treatment boils down to one underlying principle: identify foods your dog is allergic to and avoid feeding him those. "That's why the elimination diet and trial period is so essential," says Shmalberg, "as it's the only way to identify which foods, and food proteins, a dog can tolerate and which he can't." Now, if it's a food intolerance rather than an allergy (which is far more likely), a food trial is still helpful, but a simple change of diet can be just as effective. "A diet with a different composition from the one currently being fed is often enough to improve symptoms," Shmalberg explains.
Unless formulated well, with the advice of a veterinary nutritionist, many homemade diets are deficient in certain critical nutrients.
Aside from that, there are a few other tactics that come up in dealing with food allergies and intolerances. Here's a brief overview, plus considerations, pros, and cons for each.
Antihistamines and Other Medications
Antihistamines like Benadryl can minimize itching, and they're relatively safe and vet-approved for use at home. Topical anti-itch shampoos and ointments may help too—just be sure to get your vet's OK before giving your dog any over-the-counter medication or remedy. Antibiotics and antifungals like cephalexin and ketoconazole, for example, may help in the short term to treat secondary infections that occur when the skin is inflamed, "but symptoms usually recur after stopping," says Shmalberg. As for anti-inflammatory medications like steroids? "They typically don't do anything to help many food allergy symptoms," he says.
Homemade Dog Food Diets
Homemade diets are sometimes used for elimination diet food trials, and for dogs with food intolerances or allergies. It's easy to see why they're effective—the owner has total control over the ingredients. But there's an issue with homemade dog food diets. "Unless formulated well, with the advice of a veterinary nutritionist, many are deficient in certain critical nutrients," says Shmalberg, "and those deficiencies could cause issues in the long run." The preparation is labor-intensive for the owner, too.
Vegan Dog Food Diets
Likewise, vegan diets are used by some owners and veterinarians during and after food trials, but there's no evidence they're more favorable than a carefully selected diet with a single protein. (In fact, vegan diets often include a lot of different vegetable proteins.) But if a dog is allergic to multiple meats, a vegan diet is certainly one way to avoid them. Like homemade diets, vegan diets must be carefully formulated. "Some store-bought vegan diets were found to be deficient in critical nutrients, and they're really only mentioned by vets because they're becoming more and more popular among owners," says Shmalberg. "It's definitely not our top choice for treating food allergies."
Best Dog Food for Allergies
When you choose a food that's freshly prepared with a few human-grade ingredients and no artificial fillers, you can see exactly what your pup is getting.
Here are his tips for choosing a diet for a dog with food allergies or intolerances:
- Change things up If you or your vet thinks your dog has a food intolerance, it's worth it to switch to a diet with a different protein source, with varied ingredients, and maybe even a different fat level. "These diets don't need to be as simple as the ones used in elimination diets," says Shmalberg.
- Commercial food labels aren't always accurate. One 2018 research review determined, after looking at a number of studies about commercial pet foods, about 45 percent of them had unlabeled ingredients, including products claiming "limited ingredients." The review did find that diets with hydrolyzed, or chemically broken-down, ingredients didn't have near the rate of unlabeled ingredients (probably because hydrolyzation is a very technical process).
- Dog food products aren't regulated for purity. Big-batch cooking in a big plant involves a lot of heavy machinery with a lot of nooks and crannies—where it's easy for contamination to happen. "Companies that make 'hypoallergenic' or 'limited ingredient' dog foods should be following best practices to eliminate this," says Shmalberg, "but there's no oversight or regulation of the manufacturing of these types of products."
- Fresh food might be a safer bet. When you choose a food that's freshly prepared in small batches, with a few human-grade ingredients and no artificial fillers, you can see exactly what your pup is getting. Homemade dog food is one option. If you'd rather not spend time preparing your dog's food, consider a made-from-scratch, small-batch dog food delivery service that emphasizes quality and purity.