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Is My Itchy Dog Allergic to Food? (Best Research and FAQ About Food Allergies)

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Dr. Mark is a veterinarian. He has been working with dogs for more than 40 years.

Food allergies can develop in dogs of any age.

Food allergies can develop in dogs of any age.

About a fifth of all dogs will have itchy signs during their life but less than a third of them will have food allergies. If your dog is itching there are several possible reasons, and if it happens year round you need to watch them for other signs. (Year-round itchy dogs will most likely have dust mite and mold allergies.) Dogs with cutaneous adverse food reactions also:

  • have ear infections over and over
  • have skin infections and hair loss
  • bite between their toes and lick their feet all the time
  • scratch their head, face, or other areas of the body
  • have loose stools
  • vomit occasionally
  • may have weight loss or a lack of energy
  • may feel bad and even be aggressive

If your dog has those signs and you treat them for the itching, remove the houseplants and mites, and then go on giving the food they are allergic to, the pet has no chance of getting better.

So how are you going to find out what is wrong?

While your dog is on a special elimination diet they cannot eat other things.

While your dog is on a special elimination diet they cannot eat other things.

Symptoms and Causes of Food Allergies in Dogs

Can Other Allergies Cause My Dog to Itch the Same Way?

Dogs with inhalant allergies will have many of the same signs as those with food allergies. If the dog is allergic to pollens, however, it is mainly during the summer. If the dog is allergic to dust mites, houseplant molds, or insect dirt it is a year-round problem and looks similar to food allergies.

The only way to tell if it is food allergies is to put the dog on a special diet. If the dog's symptoms are gone by the time the trial is over, and the dog then starts itching again when given the old food, you will know the answer.

How Long Does It Take to Know if a Dog Is Allergic to Food?

If your dog is allergic to something he ate he might show signs right away (anaphylactic reaction, or immediate hypersensitivity) but the most common problem we see is delayed allergic reactions.

This type of reaction only happens when a dog has been exposed to a food for a long time; signs do not show up right away. Dogs with delayed reactions may have skin or gastrointestinal symptoms and will need to be diagnosed and put on a special diet.

What Is the Most Common Food Allergy in Dogs?

About a third of the dogs that are allergic end up being sensitive to beef. (1) Any kind of protein that the dog has been eating for a while can also cause problems, so we also see dogs with dairy, chicken, and lamb. (Pork, eggs, and fish have also been seen but are a lot less common.).

Dogs can also be allergic to some of the carbohydrate sources in dog food so they may have a problem with wheat, soy, or rice.

What Are the Signs of a Dog With Food Allergies?

Dogs with food allergies show signs in their skin but also have other signs:
itching: over 90% of food allergic dogs will have itching as their main symptom. (2)

  • ear infections (usually recurrent)
  • pyoderma (bacterial skin infection)
  • allergic dermatitis (red skin and hair loss around eyes, ears, lips, feet)
  • yeast infection (skin and ears)
  • vomiting and diarrhea (in one study 93% had diarrhea, 2 % had vomiting, and 5% had both) (2)
  • acting tired and grumpy
  • hot spots (less than 10%)
  • signs that have nothing to do with the skin or gut like anaphylaxis (swollen and red around the eyes, hives, vomiting, breathing problems), nail disease (symmetrical lupoid onychodystrophy), runny nose and sneezing

Are Male or Female Dogs More Likely to Develop Food Allergies?

Both male and female dogs can develop food allergies. None of the studies have shown that one sex is more likely to have problems.

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Read More From Pethelpful

What Age Are Dogs When They Become Allergic to Food?

Any age of dog can become allergic. About 40% of dogs have signs by one year of age. (2)

What Dog Breeds Are Affected With Food Allergies?

Any dog can develop food allergies, but 40% of the cases were in four breeds. (3)

  • German Shepherd Dogs
  • West Highland White Terriers
  • Labrador Retrievers
  • Golden Retrievers

So if your Lab or German Shepherd has all the signs of a food allergy and nothing else works, what is the next step?

Dog food that is stored improperly is contaminated with storage mites.

Dog food that is stored improperly is contaminated with storage mites.

Food Trials for Allergies in Dogs

How Do I Find Out If My Dog Is Allergic To Food?

The only way to find out for sure if a dog is allergic to food is to put him on a special diet and see if the signs go away. It is not enough to switch your dog to another commercial diet that is not labelled as an elimination diet. (Even about a third of the novel/limited ingredient dog foods may have other things present.) (2)

A dog on a food trial cannot eat treats that are not made up of beef or chicken. They cannot take a flavored medication like Heartgard. And unfortunately, it takes a while to find out if a dog has food allergies.

To find out if a dog is really allergic to their food, however, you need to wait for the clinical signs to go away and then feed the old food again to see if the dog gets sick again. Many people do not like to do this and will keep a special diet for the rest of their life.

How Long Will My Dog Need to Be on a Special Diet?

It takes anywhere from 3 to 12 weeks to find out for sure if your dog has a food allergy. After 3 weeks, half of the dogs had no more clinical signs. 95% were better after 9 weeks, but the rest did not clear up until the full 12 weeks. (2) If your dog does not get better you should go on with the trial until the 3 months are finished.

But how often will you have a dog with food allergies?

How Common Are Food Allergies in Dogs?

There are a lot of different numbers, but if the dogs have a skin disease that looks like allergies, about a fifth to a third of them have food-based allergies.

Even though food allergies are relatively uncommon, they are still common enough in allergic dogs to justify the trial diet. It would be better if this could be ruled out immediately though so an allergic dog could be treated for what is wrong.

Are there other things you can do to find out if a dog is allergic to food even more quickly?

Are There Other Tests To Find Out if My Dog Is Allergic to Food?

Since the elimination diet takes so long and it takes so much extra effort there has been a lot of interest in finding a faster test that works. Lab tests have not been shown to work yet.

Skin tests were sometimes positive for dogs with no allergies and sometimes negative for dogs with food allergies. Saliva tests do not work. Patch testing was okay if you were deciding what the dog had never been exposed to but was not useful for finding out if the dog was allergic.

The one test that was accurate is called the lymphocyte proliferation test. (4) It is not easy to perform and so far has only been done in university labs. The only way to tell if your dog has food allergies is to put them on a trial diet and then later expose them to the old diet to see if the signs return.

So if you want to do a trial and have not had a patch test what kind of meat do you use?

What Meat Is Best For Dogs With Food Allergies?

The protein source needs to be novel, or something that your dog has never eaten in his regular diet. Most companies do not use:

  • rabbit
  • ostrich
  • venison
  • bison
  • turkey
  • duck

If you have been giving one of these foods to your dog, however, do not use it for the trial diet.

But is it okay to just buy a bag of dog food that is made with duck or venison?

Is My Dog Allergic to the Mites In Dog Food?

Some dogs with year-round allergies are allergic to dust mites. It is possible that you can give your dog a commercial diet for diagnosing food allergies and not see any improvement because of allergies to storage mites.

Storage mites have very low numbers in a new bag of food. If the bag is kept in a warm area (like the garage in the summer) they proliferate. The more days the bag is open the more mites will be present. About 80% of dog food bags left open in warm climates have mites. (5)

A homemade diet is the best way to avoid storage mites. If you decide to use one of the commercial diets, you need to buy smaller bags, keep the bags closed, and keep them in a cool place so that the mites do not breed.

But what if I think the elimination diet is too expensive?

Duck is a novel protein source for most dogs. If your dog has been eating duck you need to search for something else.

Duck is a novel protein source for most dogs. If your dog has been eating duck you need to search for something else.

Alternatives for Food Allergies in Dogs

Are There Cheaper Foods To Find Out If My Dog Has A Food Allergy?

If your veterinarian suspects that your dog is allergic to something in his food they will put him on a special diet. The diet will contain none of the normal proteins or carbohydrates in his regular food or may even be made with hydrolyzed proteins which are broken down so that a dog will not be allergic to them.

One problem with the special diet is that it is expensive. The protein source is not something the food companies normally use so they have to buy the components in lesser quantities, which makes them more expensive. They also have to be produced in a special factory away from the other foods so that is another reason they cost so much.

If you want to find out if your dog has a food allergy but cannot afford the special diet it is possible to make up the food at home. You cannot just go out and buy chicken if they suspect a beef allergy, however. It needs to be something totally new. If your dog has never eaten rabbit, it can be a diet made up of rabbit. You can also use turkey, duck, bison, ostrich, or venison if your dog does not normally eat one of those foods.

The carbohydrate source should also be something new like sweet potatoes or pumpkin.

Buying the novel protein may be just as expensive as the diet you purchase, so if you are interested in this you need to compare the prices. I have included a video below with some instructions on how to make up the diet.

If you are going to use a homemade diet long term it will need to be more balanced but this simple recipe is fine for the month or two that you will need to use an elimination diet. This food IS NOT what your dog needs for a long and healthy life.

If your dog is food allergic and you decide to use a homemade diet long term this is a much better alternative. You will need to use more ingredients but a dog can eat this food for the rest of their long and healthy life.

Sources

(1) Mueller RS, Olivry T, Prélaud P. Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Vet Res. 2016 Jan 12;12:9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4710035/

(2) Valentine B. Review of critically appraised topics on adverse food reactions of companion animals. Can Vet J. 2020 May;61(5):537-539. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7156131/

(3) Olivry T, Mueller RS. Critically appraised topic on adverse food reactions of companion animals (7): signalment and cutaneous manifestations of dogs and cats with adverse food reactions. BMC Vet Res. 2019 May 9;15(1):140. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6507158/

(4) Mueller RS, Olivry T. Critically appraised topic on adverse food reactions of companion animals (4): can we diagnose adverse food reactions in dogs and cats with in vivo or in vitro tests? BMC Vet Res. 2017 Aug 30;13(1):275. https://pubmed.ncbi.nlm.nih.gov/28854915/

(5) Hibberson CE, Vogelnest LJ. Storage mite contamination of commercial dry dog food in south-eastern Australia. Aust Vet J. 2014 Jun;92(6):219-24. https://pubmed.ncbi.nlm.nih.gov/24862999/

This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

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