Food Allergies & Intolerances in Cats & Dogs

In cats & dogs, food intolerances & allergies often have similar symptoms but are two different conditions...

Created: 5/23/2024 Updated: 6/24/2024 - Shelley Simmons

cats, diet, Diet & Nutrition, dogs, health, Health & Wellbeing, parasite, skin

Skin conditions

Dogs can suffer from a variety of skin conditions, causing pain, itching, inflammation and significant discomfort for your pet and can indicate an underlying health condition that hasn’t already been diagnosed. Depending on your dog's breed, age, and a number of genetic factors, you may find they are prone to skin conditions.

Skin conditions can vary from mild to severe and can manifest as pruritus (itchy skin), dermatitis, otitis (ear infection), or gastrointestinal (diarrhoea) disturbances. Seeking veterinary guidance promptly is essential for accurate diagnosis and effective treatment, ensuring your pet's well-being. If a skin disease is left untreated for a while the condition can often become more complicated. For example, an allergic skin reaction may become secondarily infected with bacteria, or a bacterial infection may also become infected with yeast. Some of the most common skin disorders in dogs include bacterial skin infections, environmental allergies and parasite allergies.

Similar to humans, food allergies and intolerances in cats and dogs are two different conditions which often have similar symptoms. They are both examples of adverse food reactions, however, food allergies involve the animal's immune system, while food tolerances do not.

Food sensitivity/intolerance

Food sensitivities are more common than allergies and do not involve the immune system. They are generally triggered by the digestive system and are less serious than allergies. When your cat or dog has a food intolerance, it means that something in their food doesn't agree with their body. It does not trigger the immune system to react like a food allergy does, however, it can cause other unpleasant symptoms for your pet.

Dog itching behind ear

Food allergy

A true allergy is an immune response to an antigen (protein). In some cases, that protein can come from food and manifest as a variety of dermatological and/or gastrointestinal clinical signs. Food allergy in cats and dogs occurs when a particular component of their pet food (usually a protein) triggers the animal's immune system to react. For example, cells may release histamine, which can then lead to itching.


When an animal begins to exhibit behaviours like scratching, biting, and excessive licking of fur, accompanied by the development of red areas, it's often assumed to be due to food allergies.

However, true food allergies are relatively rare, affecting only around 1% of all dogs and cats experiencing skin issues. Food allergies rank as the third most common skin allergy, following flea allergies and atopy (sensitivities or allergies to environmental triggers such as pollen, dust, moulds, dust mites, and grass).

It's crucial to recognize that these symptoms can also arise from non-food allergies in cats and dogs, and may be indicative of other underlying health conditions. Therefore, a comprehensive evaluation by a veterinarian is essential for accurate diagnosis and appropriate management.

White cat scratching against wall

How do you identify a food allergy/food reaction

Testing for true food allergies in pets is neither simple nor straightforward, and the only recognized method is to conduct a food elimination trial, which typically spans several weeks to months. Although various commercial tests, including blood, hair, and saliva tests, are available, they are generally unreliable for accurately diagnosing the underlying cause of allergies. The results from these tests tend to be inconsistent and may not provide definitive answers.

Blood tests for allergies detect antibodies against certain food proteins, but this does not necessarily mean the pet has a true allergy. It can simply mean the pet has eaten that type of protein before.

It's crucial to understand that animals can develop allergies to foods they consume regularly; allergic reactions typically don't occur upon the first exposure to a particular food. In dogs and cats, animal proteins are generally recognized as the most common food allergens.

Foods Reported to Cause Allergies in Dogs and Cats

Seasonal and environmental allergies in dogs

Environmental allergens for dogs include pollen, moulds, grass, trees, and dust mites. Another common allergen is flea saliva, which causes a disease called flea allergy dermatitis.

If you notice that your dog suffers from itching and scratching during a particular time of year, or in response to being in a specific place, it helps to keep a diary. Diagnosing allergies is extremely difficult and involves a lot of trial and error, so gathering as much information as possible will be helpful.

ALLERGIES ARE ALWAYS IN SEASON: Over the past 10 years, we've seen a 30.7% increase in environment allergy cases in dogs and an 11.5% increase in cats. Allergens can vary by region and climate, but many common triggers can be found in the home: Dust & Storage Mites, Pollen, Dander, Mould, Fabrics, Feathers, Medications, Cleaning  Solutions (Source: Banfield Pet Hospital).

Elimination diets

An elimination diet trial is essential for removing the suspected food allergen from your cat or dog's diet. Diets selected for allergy trials must incorporate a novel protein and carbohydrate source, one that your pet has never consumed previously. Additionally, it's imperative to exclude all other food items from their diet, including treats, chews, chewable tablets, human foods, etc., and to ensure that no unnecessary medications are administered during the diet trial. It typically takes years to become allergic to a food protein so the patient should not be allergic to something new.

The elimination trial typically lasts between 6 to 12 weeks, allowing sufficient time for the body to adjust and symptoms to potentially subside. Keeping a detailed food diary during this period, documenting everything your pet consumes, their exercise routines, and any changes in symptoms, greatly aids in the diagnostic process.

After your pet successfully finishes the trial and progress has been observed, the next step is to administer a "challenge" with the suspected allergen. By introducing the food in question for approximately 2 weeks, we can monitor for any allergic reactions. This step is crucial in pinpointing the specific allergen and understanding your pet's sensitivities. Identifying the allergen enables you to safeguard your pet's health by excluding it from their diet, ensuring they remain free from discomfort or adverse reactions from the food and treats you choose to feed them.

Ginger cat licking it's lips going into the kitchen

How to follow a food elimination trial

  • Feed to ideal weight.

  • Stop all extras, treats, supplements, chews, flavoured tablets etc. and feed nothing but the recommended diet food.

  • Ensure free access to fresh water.

  • Feed for a minimum of 8 -12 weeks (if allergies get severely worse then stop and seek veterinary advice).

  • Because each animal's case is very different including the level of severity of the allergy/sensitivity, it is important to follow the protocol very closely.

  • Treatment for the itching must be managed as not to interfere with the trial.

  • Keep a diary of the animal's response whilst on the food. i.e. score itchiness, redness of the skin, behaviour (depression), licking etc. Score on a 1-10 scale each day.

  • Ensure your pet and the house have been treated for fleas. This is important even if you think your dog doesn't have them. Flea dermatitis is the most common reason for skin issues so is always worth treating to rule out any possibility.

  • It is important to have all family members on board with the trial so nobody gives any other foods or treats.

  • Ensure your pet has no access to any other animal's food in the house.

  • Diet trials may encounter challenges during seasonal transitions, especially if the animal is allergic to specific pollens, grasses, trees, etc. In such cases, a change in season can mistakenly appear to improve the diet's effectiveness when it's actually the result of environmental factors like pollen levels shifting. That's why conducting a challenge at the conclusion of the trial is crucial, even if the pet has shown positive responses throughout.

  • If the pet has a true food allergy, you would expect to see at least a 50% reduction in licking, scratching, chewing or other dermatologic signs. Signs can improve after 4 weeks but can take up to 12 weeks. Cats may need to remain on an elimination diet for 12-16 weeks before an improvement is recognised.

  • To confirm a genuine food allergy, a diet challenge should be performed. This involves reintroducing the suspected allergenic food to observe any adverse reactions in the pet. Typically, signs of allergies can show up again within hours to two weeks. It's crucial to reintroduce one ingredient at a time and maintain a two-week interval between each food, diligently monitoring the animal's response using a diary. The recurrence of symptoms upon reintroduction of a specific food is indicative of an allergy or sensitivity.

Small dog eating from white bowl

Types of elimination diets for cats & dogs

There are a few options for elimination diets, and we would always advise you to speak to your veterinary practice and nutritional advisor to help you decide on the most appropriate diet choice.

Hydrolysed diets

Hydrolysed diets are composed of very small protein molecules. The aim is for these small molecules not to be recognised by the immune system, reducing the risk of an allergic reaction.

Novel or alternative protein diet

A novel protein diet consists of a single protein source that your pet hasn't previously eaten, reducing the likelihood of developing allergies. Such proteins could range from common options like duck, salmon, venison, and whitefish to more unusual choices such as kangaroo.

OSCAR diets that may be suitable depending on the pet’s current diet include:

Grey cat itching

Home care support

  • Ensure your pet and the house have been treated for fleas (even if you feel your pet doesn't have any – all skin specialists will advise you to do this before making further recommendations or starting any treatment).

  • Ensure regular hoovering and damp dusting (not dry). Don't use sprays, carpet powders etc.

  • Avoid using scented plug-ins, stand alone sprays, incense sticks candles, wax melts etc.

  • Steam clean hard floor surfaces and clean carpets regularly (not with powders or smelly liquids).

  • Dehumidifiers can be used to combat damp and mites.

  • Avoid walking when the pollen count is high.

  • Always rinse off paws and undercarriage when the dog comes back from a walk before entering the house and use a towel (washed in non-biological powder at a high temperature) to pat dry.

  • Do not walk into the house with shoes or coats on that have been outside as this will also bring in outdoor pollens. Ensure no visitors etc. come into house with shoes or coats either.

  • Wash bedding regularly (washed in non-biological powder at a high temperature).


Food allergies and intolerances are relatively uncommon in dogs and cats and can pose challenges in accurate diagnosis. However, for any dog or cat experiencing non-seasonal itchiness, gastrointestinal disturbances, chronic or recurring otitis, or those showing inadequate response to medical treatment, a strict food elimination trial is advisable.


  1. Verlinden A, Hesta M, Millet S, Janssens GPJ. Food allergy in dogs and cats: A review. Crit Rev Food Sci Nutr 2006; 46:259-273.

3.Boehm, T. M. S. A., Klinger, C. J., Udraite-Vovk, L., Navarro,

C., & Mueller, R. S. (2021). Clinical effects of 2 commercially available diets on canine atopic dermatitis. Tierärztliche Praxis Ausgabe K: Kleintiere/Heimtiere, 49(4), 256-261. doi: 10.1055/a-1543-4743

Do you need further advice?

If you need any further advice, please contact the OSCAR Helpline Team on our freephone number 0800 195 8000 or email