What causes food allergies?

A food allergy is a reaction by an individual animal to a particular substance in their food. This occurs when the bodies’ response to normal food becomes ‘confused’, causing abnormal reactions. Frequently the food has been part of the diet for a long time. We cannot stop this abnormal reaction so the only effective treatment is to avoid eating the food that causes the problem.

The most common causes of food allergy in the dog include beef, mutton, chicken, wheat, corn, soy, dairy foods and eggs. Occasionally chemicals such as preservatives, additives or food dyes are also the culprit.

The most common causes of food allergy in the cat include fish, beef and dairy products.

What are the signs of food allergy?

The most common clinical sign of a food allergy is itching. This leads to chewing, rubbing and scratching with hair loss and redness. Some animals may have loose stools, diarrhoea, vomiting or ear infections. The signs are often very similar to the signs seen with other allergies.

How is an allergy to food diagnosed?

Unfortunately there are no reliable tests to diagnose food allergy in dogs and cats. The diagnosis is made by conducting an elimination diet trial. This involves feeding a new food that your pet has not eaten before for a period of six to eight weeks. If your pet has a food allergy, we will see an improvement in the itchiness and/or loose stools over this period of time.

What’s involved with an elimination diet trial?

For 6-8 weeks you will need to feed a new diet. We prefer you use home prepared foods, though there are commercially prepared alternatives in biscuit and tinned forms. It is essential that you feed nothing other than the trial diet. Feeding even a small amount of other foods will result in a continuation of allergy symptoms.

Food items that need to be avoided during the trial:

  • Treats
  • Bones
  • Human foods
  • Vitamin supplements
  • Toothpastes or flavoured medications (including flavoured heartworm medications)
  • Milk

Food items ok to be fed during the trial:

  • Bones (of the meat source used in the trial)
  • Jerky treats (of the meat source)
  • Unflavoured heartworm medications
  • Water

How is the diet trial assessed?

In order to diagnose an allergy to food, we need to see an improvement in the symptoms whilst on the diet and a worsening of them when we introduce other foods. The easiest way to achieve this is to record on a daily basis the symptoms (itchiness/ loose stools) and level of severity your pet has experienced. It is also important to record any foods not part of the trial that were accidentally fed. This will help us diagnose a food allergy and tell if other allergies are also present.

If a food allergy is found, a process of elimination will be used to determine which foods are causing the problem to allow a return to a more normal diet.