Food Allergy

Posted on August 26, 2016

You may have had suspicions or just been informed by the vet that your dog is likely to be suffering from food allergy, or may be at a higher risk of food allergy as compared to other dogs. So what do all these mean?


Atopy is defined as “a clinical syndrome involving allergy with a hereditary predisposition”. This means that atopic dogs are frequently allergic to what is considered to be common and harmless substances such as grass, tobacco smoke and various types of food. This also means that if your dog is genuinely suffering from a food allergy, it most likely would be allergic to other substances in the environment. These allergy traits may also be passed down to offspring.

Common clinical signs of food allergy

Food is consumed and then absorbed with the nutrients travelling throughout the body. Dogs suffering from a food allergy typically have reddened skin all over their body, including the interior of their ears and on their faces. These dogs are usually very itchy and commonly have a secondary bacterial or fungal infection superimposed on the allergy. Hence, while it is important to diagnose with a skin scraping, and then treat the infection, the primary cause of the problem is the allergy. If the allergy is not addressed appropriately, the skin infection will recur.

Occasionally, the food allergy may manifest as chronic soft stools or diarrhoea.

If your dog is suffering from redness of his/her paws, belly, and underneath the neck and jaw only, it is most likely a contact allergy rather than a food allergy.

Some treatments used in food allergies

As food allergies are essentially an “overactive” immune system, where the body’s antibodies “attack” common foodstuffs, steroids or antihistamine drugs can be used to dampen the body’s response. Tablets typically last for a maximum of 48 hours – if you stop giving these tablets, the signs will recur in less than a week. Sometimes, a steroid injection can be given to alleviate particularly bad clinical signs – however once the drug wears off (anywhere between 1-3 months) the signs will recur. While this is a highly effective treatment, long-term usage may result in side effects, including liver failure, Cushing’s disease or Addison’s disease (when the steroid is suddenly stopped).

A “drug-free” way to treat food allergy is to try to eliminate the food(s) that your dog is allergic to. Bear in mind that your dog may be allergic to more than 1 food substance. This will involve a radical change in your dog’s diet for 2 months, and is called a food trial.

Food trial

A food trial is basically a period where you attempt to feed your dog a new food substance altogether. Hence, for a food trial to work, you must be completely honest in listing out all the types of food that your dog eats, including dog snacks and human food. Your vet would then advise you of a possible novel food to feed your dog.

You will then be sent home with strict instructions to feed your dog nothing else but this new food for 2 months. This means that you cannot give your dog any commercial snacks. However, you can make your own snacks at home – thinly slice a steak of meat/fish (depending on what type of food you have been told to give as your dog’s main meal) and slow bake the slices without additive or flavouring at 60°C until dry; these snack will keep in the fridge for 1 week. Medication to treat the superimposed bacterial/fungal infection will also be dispensed.

After 2-3 weeks, if the food trial is successful, you should notice a vast improvement in your dog’s skin condition. This is not only because the infection is gone, but also because the skin is not so inflamed.

Remember that there is no dog food, commercially or home cooked, that will be suitable for all dogs. Hence the food trial may not work. This may be because your dog is allergic to the meat/protein component, or even to the additives (such as brewer’s yeast).

What if the food trial isn’t successful?

 If the food trial isn’t successful, you will then be left with 4 options:

  1. Give up and let your dog itch for the rest of its life
  2. Put your dog on long term antihistamine, drugs or steroids, with the risk of side effects
  3. Go on another 2 month food trial
  4. Run a Spot Test

A Spot Test is a blood test that we run to check what substances your dog is allergic to. It will test for various types of food, grasses and plants, and environmental substances. The results take 1-2 months to come back from the USA. Based on the test results, you can try to eliminate as many of the substances that your dog is allergic to from its life.

Will my dog be cured for life after a food trial?

Not necessarily. A few dogs will be controlled for life. Most dogs are likely to go on to further allergies. This is because after a period of being exposed to the new food, the body will start to develop antibodies against this new food and start the allergy cycle all over again. (Remember that the immune system is “overactive”.) Hence, it is important to feed only the suitable food when you have found one, and not give other forms of protein/carbohydrate/additives, or you will find it difficult to find a new food to feed your dog when the food allergy recurs. On average, food allergies recur after 2 years of feeding a new food.

Case Study

Freckle, a 3 year old, sterilized female Shih Tzu dog, had been having itchy skin and ears for 2 weeks. Her skin was very red all over and has a lot of pimples on it. A skin scraping showed her to have a bacterial infection. Her ears also had a slight yeast infection. Her owner revealed that Freckle had been having skin problems on and off since she was 6 months old. She normally gets better after an injection and some medicine and shampoo, but the skin problems recur every 3-4 months.

Freckle was diagnosed with having a food allergy. Her owner had been feeding her canned food, mixed with a Lamb and Rice dry diet. She also got liver treats in the morning. There was a suspicion that her owner’s parents were feeding beef, cake and bread while her owner was not at home. Freckle has never been fed fish.

Freckle was placed on a fish-based food trial. She was also given antibiotics and a medicated shampoo to treat the infection of the skin, as well as ear cleaning solution and medication to treat the ear infection. Because she scratched a lot and was starting to injure herself (self-trauma), she was given a 5-day course of antihistamine to temporarily alleviate the itchiness.

3 weeks later, Freckle was brought back for her review consultation. Her skin was not red anymore, but more importantly, she was no longer scratching herself. The vet knows that it is likely that her skin is improving due to the new diet and not the antihistamine because the latter was stopped more than 2 weeks ago.