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Food allergies in cats and dogs

Did someone tell you that their pet has an allergy? Did your veterinarian suggest that your pet might be having problems due to allergies? Or do you suspect that your cat or dog has an allergy? Food allergies seem to have gotten more common in the past decade and every pet owner seems to have a pet with an allergy. The reason for this increase can partly be blamed on overlapping symptoms, which makes it quite difficult to give your pet the right diagnosis. In fact, scientific research has concluded that only 1 out of 100 skin conditions in dogs and cats can be traced back to a food allergy. As the symptoms and reactions can be quite confusing, it is important to understand what type of reaction your pet has to its food.

Cat eating food

Food hypersensitivity, food allergy or food intolerance?

A lot of confusion surrounding food allergies is caused by the terms “food hypersensitivity”, “food allergy” and “food intolerance”. Even though the terms are often used to describe the same condition, they actually mean different things. Food hypersensitivity is the umbrella term for physical reactions to certain ingredients in the food; both a food allergy and food intolerance are therefore hypersensitivities.

If your pet has a food intolerance, the physical reaction is triggered by the digestive system and the reaction is usually less severe. Think of a lactose intolerance, where the body lacks the lactase enzyme; or food poisoning where a toxin in the food is responsible for the complaints.

food allergy can be traced back to the immune system, where the system identifies an ingredient as an invader. The reaction that follows can cause a range of symptoms, which can even be severe or fatal in some extreme cases. In this article we will only focus on recognising, diagnosing and treating food allergies.


Common symptoms of food allergies are mild to severe non-seasonal itching and skin conditions. This means symptoms that occur mainly around the eyes and snout of your pet, like itching, bald spots, redness or a rash. Some of the symptoms are a lot more subtle, like ear infections or a flaky, oily coat. About 15% of the time, these symptoms are accompanied by gastrointestinal issues like vomiting after eating and/or diarrhoea. Colitis or an increased frequency of defecation can occur as well. Some dogs will lick their paws of rub their nose on the floor. Cats are more likely to experience scabs, symmetrical baldness, eosinophilic granuloma complex (skin lesions), and/or extreme itching on the neck and head.
Unfortunately, these symptoms can also be linked to other conditions. Itching, skin changes and licking are seen in atopy. Yeast infections (Malassezia pachydermatous) are quite common as well. As both young and senior pets can suffer from food allergies, it’s difficult to link the allergy to a specific age. Most pets do develop an allergy around their second year, but there are also pets that have a sudden allergic reaction to food they’ve been eating all their life. All these factors make it really difficult to determine whether your cat has a food allergy or another health condition.


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Allergic reactions are usually triggered by a protein source and in some rare cases a grain source. These substances that cause the reaction are called allergens. The most common allergens in dogs are beef, chicken, egg, corn, wheat, soy and milk. Cats are usually allergic to fish, beef, milk and chicken. In general, dogs and cats are allergic to a range of 1 to 5 allergens.


The only way to diagnose a food allergy is to prescribe your pet a special diet. This is because blood samples aren’t really reliable in diagnosing an allergy. There are three types of elimination diets: a home-made diet, a diet based on a novel protein source, or a diet with hydrolysed protein.

Homemade elimination diet

A homemade diet consists of a novel protein source (i.e. a protein your pet hasn’t eaten before), as well as one carbohydrate source. Potato or rice is usually used as the carbohydrate source, whereas the animal derived protein is usually ostrich, deer, rabbit or horse. A downside of homemade diets is that it can be tricky to get all the right ingredients in – there is often a lack or overdose of certain nutrients. These can cause a dull coat, hunger, skin flakes and weight loss. To make sure your pet gets enough nutrients, you can add a TROVET supplement to the diet. Another downside is that preparing these diets yourself can take a lot of time, and that certain ingredients might not even be available to you. In that case you can add the ready-made TROVET Unique Protein source. You can then complete the food by adding your own carbohydrate source like rice or potato.

Prescription diet

A second option is a ready-made prescription diet. This type of diet also uses a novel protein source that your pet hasn’t eaten yet. These diets are commercially manufactured, which means that they contain all the essential nutrients. Examples of these are the TROVET Hypoallergenic diets, the Virbac Veterinary HPM Allergy diets or the Hill’s Food Sensitivities prescription diets.

Prescription diet based on hydrolysed protein

Another option is to use a diet with hydrolysed protein. This means that the protein is cut into tiny pieces, so the body doesn’t react to it anymore. Royal Canin’s Hypoallergenic diets, Vetality Hypoallergenic Dog Wet and Hill’s z/d prescription diets are made with hydrolysed protein sources.


Please note

The hypoallergenic diets need to be prescribed for 6 to 8 weeks. If the symptoms disappear after this period, it is very likely that your pet has a food allergy. The definitive diagnosis can only be given after challenging your pet – this means feeding your pet the food that he was eating before the diet. If your pet has an allergy, the symptoms will return within 1 hour to 14 days.

During the period that pets are prescribed a diet, they aren’t allowed to eat anything apart from the hypoallergenic food. This means no treats, cookies, pieces of bread or leftovers. While this might seem harsh, you’ll actually be protecting your pet from eating food that can cause an allergic reaction. Even medication with a special flavour can interrupt the diet, like beef-flavoured deworming treatment. If your pet is on any corticosteroids or antibiotics before starting the hypoallergenic diet, it will take about two weeks for the diet to take effect.

Do you have questions about food allergies or food hypersensitivities in dogs or cats? Contact our veterinarian via e-mail at:!