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Food Allergies (Adverse Food Reaction)

An adverse food reaction (food allergy) is a reaction to a particular food substance.

Overview

Food allergies represent one of the most common types of allergies in cats and dogs.

In animals food allergies can manifest in several problems such as:

• Itchy skin, which can lead to skin infections
• Ear infections
• Gastrointestinal disturbances
• Anal gland problems
• Hair loss (alopecia)

Adverse reactions to food can be generalised, showing a range of signs or localised to the feet, face, ears, anal glands and abdomen.

It can take months or years before your pet develops an allergic response to a particular food, and the age of onset can vary anywhere between 4-months to 14-years. 

Causes

Common food allergens:

• Fish
• Beef
• Cow's milk
• Chicken
• Soy
• Corn

Studies show that nearly 90% of all food allergy cases were from fish, beef, and dairy products.

The most common food allergens in dogs include beef, wheat and dairy, and in cats it can include fish, beef and dairy. Chicken, lamb and soy are also relatively common allergens. The allergy is to a particular ingredient in the food, so just switching brands of food is generally not enough. 

Management

There is no specific test to diagnose food allergies. The only method of confirming a food allergy is via an elimination diet trial. 

Veterinary management of allergic signs may include:

• Prescription diet
• Medicated shampoos
• Medicated creams
• Antihistamines
• Corticosteroids
• Cyclosporine
• Fatty acid dietary supplements

Diagnosis

An elimination diet trial or "food trial" is required to diagnose a food allergy. Your pet will be provided with a novel protein diet that they have never been exposed to (homecooked or commercial), which must be strictly adhered to for 8-12 weeks. It is the removal of the food allergen that leads to an improvement of signs within 4-12 weeks. 90% of adverse food reactions can be diagnosed after 8 weeks.

Elimination Diet Trial 

• The elimination trial involves feeding ONE novel source of protein and ONE novel source of carbohydrate (ie: something your pet has never been exposed to).
• This can be challenging as most dogs and cats have eaten commercial diets containing a mixture of different protein and carbohydrate sources (take a look at the ingredients list on the back of your pets food packet).
• Possible options for protein are kangaroo, horse, venison, turkey, duck, emu and goat. The choice of meat can be fed cooked or raw.
• Possible options for carbohydrate (dogs only) are potato, pumpkin, sweet potato / kumara or lentils. Vegetables are ok, but exclude corn and onion. Do not offer pasta or rice. 
• Alternatively, you can use a commercial prescription diet which has altered protein and carbohydrate molecules which prevents the body recognising and reacting to these molecules.
• Elimination diets should be fed for a minimum of eight weeks, ideally ten. 
• It is important not to feed anything else but the discussed diet. ALL TREATS must be excluded including rawhide chews, flavoured dietary supplements, toothpastes and even flavoured medications / worming. 

Confirming Food Allergy 

During a food trial it is important to monitor clinical signs and assess whether or not your pet is improving. A diagnosis of food allergy is only confirmed if the problem returns (if it had stopped during the trial) when your pet is reintroduced to their original diet. The original diet should be re-fed for 14 days but stopped immediately if reaction is noted. NB: If the problem doesn't return with reintroduction of the original diet, it is possible the allergy was due to something else in the environment that has since gone away. 

When a food allergy is confirmed and the clinical signs have resolved again by being placed back on the test diet, we can start to identify specific food allergens. This is done by adding one pure ingredient at a time to the test diet to determine which individual allergen(s) is/are the culprit.

30 - 60% of food allergic dogs are reported to be allergic to more than one food item, so it is important to test each major food ingredient that was contained in the original diet. Once we determine what food(s) your animal is allergic to, we can formulate a long-term diet management plan. 

If there is no improvement on the food trial then a food allergy can usually be ruled out. However some proportion of dogs with food allergies will still react to the commercial food trial diet and will require a home cooked diet only. 

It is also possible for an animal to have multiple allergies concurrently, ie to both a food and an environmental allergen, and therefore a multifactorial approach to skin issues may be needed. This may be the case if your pet improved with the treatment trial but the clinical signs didn't completely go away. 

Weight	Protein Source	Carbohydrate Source	Total
5kg	130g	270g	400g
10kg	200g	400g	600g
15kg	260g	540g	800g
20kg	400g	800g	1200g
30kg	520g	1080g	1600g
50kg	830g	1670g	2500g
70kg	1200g	2300g	3500g

Commercial Diets for Elimination Trial (in no particular order)

• Hills Derm Complete
• Hills Prescription Diet Z/D
• Royal Canin Veterinarian Anallergenic
• Royal Canin Veterinarian Hypoallergenic
• Delicate Care Sensitive Skin & Stomach
• SKD Crocodile & Tapioca roll
• SKD Salmon & Tapioca roll
• SKD Wildboar & Pumpkin roll
• SKD Kangaroo & Pumpkin roll 

Tips

Tips to help reduce food allergy symptoms

• Strict diet avoiding known food allergens.
• Avoid treats.
• Frequent bathing with natural soothing products such as aloe vera and oatmeal for healthy skin, finishing off with a soothing leave-in conditioner.
• Dietary supplements such as Omega 3 (DHA & EPA) for healthy skin.
• In the case of wheat allergies, consider diets with carbohydrates sourced from potato, rice, or corn, avoiding wheat, barley, rye, and oat.