Does Your Pet Have a Food Allergy?
This article is written by Pet Circle veterinarian, Dr Kim Chainey and updated by
Are you suspicious that your pet may have a food allergy? Food allergies are responsible for approximately 10% of allergy cases in dogs, ranked third after flea allergy and atopic dermatitis (airborne allergies) - although food allergies are a little more common in cats.
Strictly speaking, we should call food allergies an adverse food reaction because it occurs when the immune system reacts to a particular pet food ingredient. The incriminating component of the food is usually the protein source - for example chicken, beef, soy, or dairy. These proteins usually resist the heat of cooking, stomach acids, and intestinal digestive enzymes, and make their way to the bloodstream and target organs where they can cause an allergic reaction. Most pets that develop food allergies, do so over a period of months or years of being exposed to a particular food.
For more info on itchy skin management, check out our articles How to Stop Your Dog Scratching, The Best Dog Food For Skin Allergies, and The Causes of Itching in Cats.
Contents:
2. How is a Food Allergy Diagnosed?
Signs of a Food Allergy in Pets
Pets with adverse food reactions will display these signs all year round, unlike other causes of itchy skin such as environmental allergens which may flare up during spring.
Pets of any age can develop adverse food reactions however, it's more common in puppies and young adults and we usually see signs before 3 years of age.
How are Food Allergies Diagnosed?
If your pet has itchy skin due to allergies, it can be difficult to determine the underlying cause. Flea Allergy Dermatitis (FAD) is the most common cause of itchiness in dogs and cats, so it is important to rule this out first when investigating any potential allergies. Make sure your pets flea prevention is up to date with a regular preventative such as Nexgard Spectra or Bravecto.
If your pet is still itchy and fleas are no longer part of the equation, your best bet is to consult your veterinarian for further advice. They may recommend a dietary trial.
Our Top Recommended Flea Products
What is a Dietary Trial?
A 'dietary trial' or an 'elimination diet' is used as part of the diagnostic process to pinpoint which allergen your pet is allergic to.
The 3 Options For A Dietary Trial
- A Novel ("new") Protein Diet
- A Hydrolysed Diet - these are prescription/veterinary diets which can only be recommended by your veterinarian
- Home-cooked diet
The chosen diet must be fed exclusively for a minimum of 6 weeks, with absolutely no treats or tidbits as this may affect results. All other flavoured tablets (e.g. heartworm prophylaxis), flavoured antibiotics and vitamins, toothpastes, pigs ears and rawhides must be excluded. (Every family member should be aware of how important this is!)
If the symptoms improve after 4-6 weeks on the dietary trial, you can assume a food reaction was responsible for your pet's symptoms. You can then introduce one ingredient per week (for example, try chicken the first week, then beef the next week, etc) and observe for a reaction. This allows you to pinpoint what your pet may be allergic to.
In reality, if the symptoms have resolved with the new diet, it may be fed long-term, as long as it is complete and balanced.
So which diet do we choose? While there are advantages and disadvantages to each, the most important factors to initially consider are: What am I currently feeding and what is the protein source? And what other treats or table scraps am I feeding? This will then allow selection of a truly novel protein source.
1. A Novel Protein Diet
What is it? A diet containing a new protein source that hasn't been fed before, such as venison, rabbit, or seafood.
Pros: Commercially available, highly palatable, easy to use, affordable
Cons: Choices have become more limited due to expansion of pet food industry; protein sources that were once "unusual" are now more common
Examples: Hill's Prescription Diet d/d, Zignature Grain Free Kangaroo, Open Farm Grain Free Salmon, Prime Air Dried Duck and K9 Natural Lamb Feast
2. A Hydrolysed Diet
What is it? A diet in which the protein source is broken down into smaller molecules that are less likely to trigger an allergic response.
Pros Commercially available - however must be prescribed by a veterinarian. Avoids pet food additives that might have the potential to cause an adverse reaction.
Cons: More expensive, reduced palatability, and a lack of evidence documenting whether dogs allergic to the parent protein will actually tolerate a hydrolysed product.
Examples: Hill's Prescription Z/d, Royal Canin Hypoallergenic, Royal Canin Anallergenic, Royal Canin Sensitivity Control
3. Home-Cooked Diet
What Is it? A diet prepared at home with a novel protein and carbohydrate source.
Pros: Can be prepared affordably depending on the recipe.
Cons: Contraindicated in growing animals due to risk of skeletal and organ pathology if incorrectly formulated or balanced, not recommended in cats, not recommended for long-term feeding
Examples: Usually consists of 1 protein and 1 carbohydrate source e.g. Salmon and potatoes. For a balanced recipe, we recommend consulting with a veterinary nutritionist.
Hypoallergenic Diets
If your veterinarian has recommended a prescription or veterinary hydrolysed diet, it's likely that they've recommended one of the following varieties. But what's the difference? See the following table which highlights the characteristics of each:
| Name of Food | Type | Prescription required? | Suitable for... | First 5 Ingredients | How does it help the skin? |
|---|---|---|---|---|---|
Royal Canin Anallergenic |
Hydrolysed diet |
Yes |
Elimination diet trials / Severe food allergies |
Maize starch, feather hydrolysate with low molecular weight, copra oil, soya oil, minerals |
The hydrolysed formula prevents any reaction in dogs where food allergy is the primary cause |
Royal Canin Hypoallergenic |
Hydrolysed diet |
Yes |
Elimination diet trials / Severe food allergies |
Rice, hydrolysed soya protein, animal fats, minerals, hydrolysed poultry liver |
The hydrolysed formula prevents any reaction in dogs where food allergy is the primary cause |
Hill's Prescription Diet Z/D |
Hydrolysed diet |
Yes |
Elimination diet trials / Severe food allergies |
Corn Starch, Hydrolyzed Chicken Liver, Soybean Oil, Powdered Cellulose, Calcium Carbonate |
The hydrolysed formula prevents any reaction in dogs where food allergy is the primary cause |
Royal Canin Skin Topic |
Skin Care Diet (Prescription) |
Yes |
Moderate Skin Conditions such as atopic dermatitis, flea allergy dermatitis, and pyodermatitis |
Dehydrated poultry proteins, rice, maize, wheat, animal fats, hydrolysed poultry liver, soya oil, vegetable fibres |
Contains the exclusive DERMAUXILIUM complex for dermatological care. High quality protein. |
Hills Prescription Diet Derm Complete |
Skin Care Diet (Prescription) |
Yes |
Moderate-severe Sensitive Skin - Dry Skin, Contact or Seasonal Allergies |
Brown Rice, Brewers Rice, Egg Product, Rice Protein Concentrate, Soybean Oil, Flaxseed, Hydrolyzed Chicken Flavor |
Skin barrier support with added bioactives and phytonutrients, antioxidants (Vitamin E) + omega fatty acids |
For more info on long term nutritional management of itchy skin, see our article What is the Best Dog Food for Skin Allergies?
Further Reading
How To Get Rid of Fleas in Dogs
Stop the Scratching: Cures for Skin Allergies in Dogs
How to get rid of fleas on your cat once and for all
Know Your Parasites: Fleas, Ticks, and Worms
Complete Guide to Cat Flea and Worming Treatments
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