What are food allergies?

A food allergy is a hypersensitivity reaction in the immune system that occurs when exposed to a certain food. These foods cause the dog’s immune system to overreact and lead to itching, secondary infections, gastrointestinal symptoms, and other health problems. Food allergies should not be confused with a food intolerance, such as a lactose intolerance.

What are the symptoms of food allergies in dogs?

The most common symptom of food allergies in dogs is itching. Most often, the itching is on the paws, face, ears, belly and under the tail. Secondary infections with bacteria and yeast are also very common in these areas and can worsen the itch from allergies.

These symptoms can start at any age, no matter if the pet has eaten the same food or lots of different food throughout their life. The most common age for food allergies to develop is less than one year old, but it can start at any age.

Other common clinical signs of food allergies include:

  • Vomiting and diarrhea in up to 20% of food allergic dogs
  • Conjunctivitis (red eyes)
  • Hives
  • Sneezing
  • Increased frequency of bowel movements (1-2 times per day is considered normal)

What are the most common foods dogs are allergic to?

Dogs are most often allergic to proteins. The most common foods identified as triggers in dogs with food allergies are:

  • Beef (34% of dogs with food allergies)
  • Dairy (17% of dogs with food allergies)
  • Chicken (15% of dogs with food allergies)
  • Wheat (13% of dogs with food allergies)
  • Lamb (5% of dogs with food allergies)
  • Less common allergens include soy, corn, egg, pork, fish and rice.

How are food allergies in dogs diagnosed?

The most accurate way to diagnose a food allergy is to perform an elimination diet trial for a specific period of time, typically 2 months, with a prescription diet under the supervision of your veterinarian. There are many diets available for helping diagnose a food allergy, including hydrolyzed protein diets or novel protein diets. Hydrolyzed protein diets are specialized kibble in which the protein that makes up the nutrient source has been broken down into such small amino acid chains that the immune system does not recognize the original protein source, so the animal is less likely to have an allergic reaction to the food. Novel protein diets are a protein source that the animal has not been exposed to before and can be fed as either a prescription kibble or canned food, or as a specially formulated home cooked diet. At the end of the diet trial, the diagnosis of a food allergy comes when the original food is reintroduced and a flare of itching, infection, or tummy upset occurs.

Key concepts to understand about an elimination diet trial:

  • Over the counter diets that claim to be “single protein” or “limited ingredient” have been found to contain ingredients not listed on the bag in up to 83% of diets studied, and therefore cannot be reliably used to perform an elimination diet trial.
  • All other foods must be “eliminated” during the elimination diet trial. Talk to your veterinarian about what treats, table scraps, dental chews, or foods to hide medications you are giving and what to do during the diet trial.
  • If your pet is still itchy at the end of the diet trial, it does not mean they cannot have a food allergy. Typically, this means there may be an environmental allergy that also needs to be addressed. How much WORSE a pet gets when the original food is reintroduced at the end of the diet trial is how we determine if there is a food allergy.

Can we skip the elimination diet trial and just do a blood, saliva or hair test for food allergies?

Unfortunately, at this time, there is no blood, hair, or saliva test that is reliably accurate in diagnosing food allergies, and therefore are not recommended.

I have changed my pet’s diet using multiple store-bought diets. Why do I need to do a diet trial?

Frequently, we see our clients attempt multiple diet changes with over-the-counter diets. If your pet has a true allergy, over-the-counter diets will likely not resolve their allergies. There are also concerns that the many available minimally-regulated pet foods might contain unlabeled food sources that could negate your attempt of a diet change for your allergic pet. An unknown ingredient within an over-the-counter pet diet can lead to allergic reactions in your pet. Think about this the same way you would think about a person with a peanut allergy. Commonly, pet food is processed in a facility where many diets are made using the same machines just like many candy bars are made in facility where nuts are present. Though the candy bar does not have nuts added in, there is a label that warns of the potential that peanut residue could have contaminated the candy bar. In the pet food industry, there are minimal regulations and requirements for this to be written on a pet food label.

Here is an example of how this could play out:

You identified that your pet gets itchy, ear infections, and a red belly after feeding them chicken, so for years, you have fed them an over-the-counter fish-based diet. Recently, your pet’s fish diet goes on back order and you switch to a new fish-based diet.

Unbeknownst to you, this new diet has unlabeled chicken in it due to the way the food is processed. Within the week, your pet is itchy, has ear infections, and their belly is red.

The same scenario can play out for years. Despite their owner’s best attempt to avoid certain foods, a small amount can slip in, leading to years of suffering.

How are food allergies treated?

Because it can take 8 to 12 weeks before itching associated with food allergies improve, your veterinarian may recommend anti-itch treatments to help keep your pet comfortable while we work to figure out if your pet has a food allergy. Medications commonly used for the treatment of itch associated with allergies include:

  • Cytopoint (Lokivetmab) Very Safe, Monoclonal antibody used to block an itch mediator from conducting the itch signal. Will make most dogs stop itching for a few weeks.
  • Apoquel (Oclacitinib) Safe, Janus-Kinase inhibitor used to block the body’s production of immune messengers (Cytokines) involved in itch and to a lesser extent, inflammation. Blocks itching quickly for up to 18 to 24 hours. Cannot be used in dogs less than 1 year of age.
  • Atopica (Cyclosporine) Mild to moderate side effects, calcineurin inhibitor used for inflammation (swelling, redness) and itching. It targets the white blood cells which lowers the production of immune mediators involved with the symptoms of food allergies.
  • Glucocorticoids (Prednisone, Prednisolone, Methylprednisolone, Triamcinolone, Dexamethasone) Mild to severe side effects that are dependent on dose and duration. These medications have receptors all over the body and target many aspects of the immune system reducing itching, inflammation and blocking allergic reactions.
  • Anti-histamines (Benadryl, Zyrtec, etc) Very safe. Histamine type-1 (H1) receptor antagonists (block histamine). The majority of dog’s symptoms of food allergies do not respond to anti-histamines due to great variability in oral absorption seen in dogs.

Other pets may develop infection because of food allergies. Infections may be treated with any of the following:

  • Antibiotics Typically, an oral medication that may have side effects and treats bacterial infections. Bacterial resistance to antibiotics may develop over time and more aggressive antibiotics with riskier side effects may be needed.
  • Antifungals Typically, an oral medication that may have side effects and treats yeast infections.
  • Topical Antimicrobial shampoo, mousse, spray, lotion, or ointment.
  • Ear medications and cleaners Most ear infections are best treated with ear drops and cleaners applied by the pet owner at home or long-acting gels applied by the veterinary staff in the hospital.

Some animals have an allergy to storage mites in kibble, and not to the protein in the kibble. In these animals, the following steps can be helpful in reducing the exposure to storage mites:

  • Do not stockpile food. Purchase only what is needed to maintain a 30-day supply or less.
  • Prior to purchase, check the bag for holes or tears.
  • Store pet foods in airtight containers in a cool, dry environment.
  • Divide the bag of pet food into one-week portions and place into freezer-safe storage containers. Keep the container of food in the freezer until it is needed to prevent mite contamination.
  • Wash food storage containers frequently with detergent and hot water. Dry completely before refilling.
  • The best treatment for food allergies is avoidance. Working with your veterinarian to diagnose a food allergy and figure out exactly what your pet is allergic to will help minimize the number of medications your pet will need throughout its life to be comfortable.

Your Vet Wants You to Know: Food Allergies Podcast Episode