Food Allergies in Cats and Dogs

‘My dog is allergic to X’ and ‘My cat is allergic to Y’ is not an uncommon statement in the world of pet care, and nutrition.

Replace X and Y with pretty much any ingredient you see on the back of a pack or tin of pet food (Chicken? Beef? Rice? Wheat… the list goes on), and you will realise why some pet owners see food as a minefield of bad skin and upset guts, just waiting to happen.

But let’s pick this apart if we can.

Signs of allergy

The word ‘allergy’ carries a lot of weight in veterinary fields: vets take it very seriously as the condition means a very uncomfortable patient. Signs you might see in a pet with an allergy include:

  • Scratching (as a result of itchiness)
  • Redness: skin irritation, and then broken skin with scabs or hair loss in the red areas, particularly where intense scratching or licking has occurred
  • Sometimes pimples, ‘hot spots’, dandruff
  • Sometimes ear problems (scratching these, smelly, moist ear canals)
  • Sometimes gastric upsets:
    • Increased number of poos
    • Loose stools
    • ‘Rumbling tummies’

From the above list, you can see there are a number of signs, and many of these can be due not only to an allergy, but due to a number of other common causes, and this is where the difficulty lies. Quite often we need to eliminate the other causes of these signs and or, hone in on the exact triggering ‘allergen’ (the causative agent of the allergy) to get to the bottom of the issue, and then to manage it.

From allergy to specifically FOOD allergy

Just like with us, our dogs and cats can become allergic to a number of things in their life. It might be the saliva from a flea that has recently bitten them, dust, grass or pollen in the environment (it’s  everywhere!) or even simple contact with chemicals, medications or items in the house that can trigger the reaction.  In some circumstances food can be the trigger.

A true ‘Food Allergy’ is defined as an “all immune-mediated reaction following food intake.” Its an intentional move by your dog or cat’s immune system to rid itself of a certain protein source that it has been fed in the past. The key recognition here is that it’s a quite specific ‘blip’ in their system, and in actual fact, food allergies are quite rare.  Amongst dogs presented to the vet for skin issues, a big global study showed that 1-2% had a food allergy, and that the number drops to 0.2% for cats. Dogs are much more likely to be allergic to something in their environment (we call this atopy), and cats are more likely allergic to fleas (flea allergy dermatitis).

Let’s not confuse ourselves: It’s more often a case of intolerance

If we look again at the list of signs that our dog or cat may show (above) we may realise that the symptoms of allergies are similar to those we see with what we call food intolerances, particularly when we’re seeing a gastro-intestinal upset. This is a much more common and straight-forward bodily reaction to foods.  Your dog or cat quite simply are unable to digest (absorb and take nutritional value from) their food. This means it passes through their system ineffectively and comes out the other end (and sometimes is even vomited) in a not-so-pleasant form. We’re talking diarrhoea.

Seeing as they can look the same, it’s common to get confused and/or use the terms ‘allergy’ or ‘intolerance’ or ‘sensitivity’ or even ‘hyper-sensitivity’ interchangeably.  Vets often refer to ‘Adverse Reactions to Food’ which makes it even more confusing. All in all, we should be careful with our language and not jump to conclusions, pointing to one product or another as ‘bad’ or ‘unhealthy’ to our pets without going through the right investigative process (below). It’s very easy to think that your dog has an ‘allergy to beef’ when in fact they have had an episode of intolerance, where for one reason or another, a meal with beef in it simply hasn’t been processed by the body as it should’ve done. Simply eating too much of that beef-containing meal can be the actual problem, for example.

Making a diagnosis, and managing a food allergy

A definite diagnosis is in your vet’s hands, but will require a lot of support, monitoring and investigation on your behalf. Your vet will likely mention the need for an Elimination Diet Trial, where owners are asked to exclude all potential offending foods and feed a specifically recommended diet for a dedicated period of time, generally at least 6-8 weeks. This takes a lot of commitment of course, as nothing else (treats, snacks, rewards, leftovers) can pass your pet’s lips during this period.

Moving forward, if you have diagnosed a true food allergy and identified the offending ‘allergen’ (normally a protein ingredient), it’s a matter of avoidance from there on in. Your vet will help you find the most appropriate diet, whether it be from the many commercial diets on the market, or a balanced home-made meal.

Help is always at hand

So, while allergies as a group of conditions aren’t an uncommon occurrence, food allergies in fact are quite rare. All can lead to terrible skin, and sometimes serious gastro-intestinal signs which compromise the health, wellbeing and happiness of your pet. Plus, it’s a major concern for you.

As per other medical conditions, it’s always best you speak with your regular veterinary clinic if you suspect an allergy is bubbling away under the skin of your four-legged friends. With their help, we can all be confident we’re feeding our pets to the very best of our abilities.

This means feeding not only their hunger and their nutritional needs, but feeding their skin, their guts, their whole bodies into a better state of health.



Olivry, T & Mueller, R. (2017) Critically Appraised Topic on Adverse Food Reactions of Companion Animals (3): Prevalence of Cutaneous Adverse Food Reactions in Dogs and Cats, BMC Vet Res. 2017 Feb 15;13(1):51. doi: 10.1186/s12917-017-0973-z.