Food Allergies: How do I know if my dog is allergic to their food?

Posted by MyDogDoc on

Did you know?

  • Food allergies in dogs often cause intestinal problems and diarrhoea, but it may surprise you to learn that food allergies commonly give dogs itchy skin.

  • Food allergy accounts for approximately 5% of skin conditions in dogs. These often occur in conjunction with other allergic conditions.

  • The only way to diagnose food allergies is to feed a strict diet that we know your dog will not be allergic to – a hypoallergenic diet - for at least 8 weeks.

  • The good news is though that once diagnosed food allergies are one of the easiest and most successful skin conditions to treat.

My dog’s food hasn’t changed for years - can they still have a food allergy?

Yes, food allergies can develop at any stage in a dog’s life but most commonly start when a dog is less than a year old.

In dogs it is usually a protein in the food that causes the immune reaction. The most common foods that dogs react to are beef, dairy, chicken, gluten and lamb.

How do I know if my dog has an allergy to food?

Most dogs will have a reaction to food (or something they’ve scavenged on a walk!) that disagrees with them at some point in their lives which is usually a sensitivity and not a true allergy. This usually causes a mild tummy upset. This is similar to humans who eat something that doesn’t agree with them.

When a dog has a true allergy, their immune system is over-reacts and produces antibodies against things that should be harmless – for example proteins in beef. This causes the body to have an allergic reaction against what should be a harmless food.

The most common symptoms of a food allergy are skin problems, such as itching, redness and rashes. Some dogs also show and digestive tract problems such as vomiting, diarrhoea and excessive gas. Dogs often have a combination of skin and digestive signs.

Can we do any tests to diagnose food allergies?

Unfortunately there are currently no reliable blood or salivary tests to diagnose a food allergy in dogs. Some newer blood tests can help to predict the most suitable diet to use for an elimination diet trial, but they cannot diagnose the food allergy and are often expensive.

What is an elimination diet trial?

An elimination diet is when you feed only one very bland diet for at least 8 weeks and nothing else. These ‘hypoallergenic’ diets contain one type of novel protein e.g. Salmon which your dog has not eaten before.

What is a hydrolyzed diet?

If we cannot find suitable foods or diets that they haven’t had before then we advise a ‘hydrolyzed’ prescription diet. This is a food where the proteins in the diet have been broken down, so they are so small that the immune system doesn’t react to them.


Diagnosing is the tricky part of the condition as the special diet needs to be fed for 8-12 weeks with no treats, titbits or flavoured medications and only water to drink. Even a tiny treat can set the investigation back to day one!

We can confirm a food allergy when the dog improves on the diet trial. We would then expect the symptoms to return if the dog starts eating the original food again.

It is important to seek veterinary advice before you start this and it should be noted that not all diets labelled ‘hypoallergenic’ will be suitable to use in your dog’s individual case.

The good news is that once a food allergy diagnosed it can be easily managed! Many dogs end up staying on the hypoallergenic diet that was used during the diet trial for the rest of their lives.

Allergic skin disease Dog Dog diets Dog food elimination diet Food allergy Health Hydrolized diet Hypoallergenic Immune Nutrition Skin condition Skin disease tummy pain

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