Three common food allergies in pets

food allergies in pets
(Image credit: Getty)

Food allergies in pets are not that common, but they’re often the first thing your vet will investigate when a pet allergy is suspected. Why? Well, environmental allergies have to be diagnosed by exclusion which means everything else should be ruled out first. Food allergies are theoretically easy to diagnose and treat- but there are some common pitfalls you should be aware of. We’re going to look at the most common food allergies, as well as how you can help your pet. Should you need some advice on hypoallergenic foods take a look at our guides to the best dog food for allergies and the best cat food for allergies.

1. Allergies to beef in cats and dogs are the most common

Beef allergy is thought to be the most common food allergy in cats and dogs, accounting for around a third of food allergies in dogs, and a fifth in cats. It’s not known why allergies to beef are so common in our pets. Symptoms of a beef allergy, as for all food allergies, include itching, skin disease, and gut problems such as upset stomachs and loose stools. Be aware that beef is included in a lot of pet foods and pet treats, so it can be hard to eliminate from your pet’s diet.

2. Allergies to dairy products in cats and dogs

The second most common food allergy in dogs is dairy products, although not so for cats. What’s important to remember is that allergies are not the same as non-allergic intolerances. Both cats and dogs are, to an extent, lactose intolerant. Their bodies do not produce enough – lactase  the enzyme needed to digest lactose – for them to be able to drink milk as efficiently as we do. But food allergies are different – these are dogs whose immune system actually attacks a protein in dairy products. Since dairy products are currently thought to be the second-most common food allergy in dogs, and most cats and dogs are intolerant anyway – it’s probably a good idea to avoid as much as possible.

3. Chicken allergies are the third most common food allergy in pets

Both cats and dogs are commonly allergic to chicken, with around 15% of dogs and 5% of cats with food allergies suffering with a chicken allergy. Ironically, chicken is one of the most common ingredients in ‘sensitive’ diets and is often suggested to be fed to dogs suffering with soft stools. If your dog or cat has recurrent gut trouble that could be associated with an allergy, chicken is probably best avoided – try going for a fish-based sensitive food instead.

What you and your vet can do to help food allergies in pets

If you think your pet has a food allergy, you might have considered changing their food. And if you’ve asked online, you’ve probably been told to avoid certain foods such as grain or feed certain diets such as raw food in order to keep your dog allergy-free. But what can you really do to help your pet?

food allergies in pets

(Image credit: Getty)

How to tell what food your cat is allergic to

Animals are allergic to proteins. And, contrary to what you might imagine, animals can only be allergic to proteins they’ve had in the past. Many people think food allergy isn’t to blame because their pet hasn’t changed food recently, but that’s not how food allergies work. In fact, most cats and dogs have been fed the food for 2+ years before signs of a food allergy develop.

Since the awareness of food allergies has increased, tests have been suggested to help to diagnose which proteins your pet is reacting to. Unfortunately, these tests are not very helpful in diagnosing food allergies. Blood tests and patch tests have been shown to be very unreliable, and shouldn’t be used to diagnose a food allergy. Saliva tests are new on the scene – they’re showing some promise, but need a lot more investigation before they’re recommended.

If you suspect a food allergy in your pet, talk to your veterinarian about starting a diet trial to diagnose your dog or cat’s allergies. This is theoretically easy, but a bit harder in practice. You will need to feed your pet a novel protein or hydrolysed diet for 6-8 weeks, and possibly up to 12 weeks. In this time, they can’t have any titbits, treats, or medications that use flavorings that aren’t okayed by the vet. Definitely easier said than done!

What’s the difference between a hydrolysed diet and a novel protein diet?

When diagnosing food allergies in pets, you’ll be given the choice of a hydrolysed protein diet such as Hills z/d or Royal Canin Hydrolysed, or a novel protein diet. Hydrolysed protein diets are generally easier. Since animals are allergic to proteins of a particular size, in these diets the proteins are broken up until they’re too small to set off the immune system. A novel protein diet means feeding a protein that your pet has never contacted before. This means you need to know your pet’s entire dietary history, right from weaning. Which is why swapping diets constantly in the hope of finding one that works is a bad idea. 

You’ll then need to work out which proteins are in your pet’s food, but this can be difficult, too. Your pet’s food probably says a flavour, such as ‘beef fillet’ or ‘salmon and vegetables’. If you look at the ingredient list, you’ll see this in more detail – it might say ‘40% chicken meal’, or it might say ‘meat and animal derivatives’, which isn’t very helpful. 

Even if it lists the exact ingredients, it might still contain other proteins – one study found that 10 out of 12 diets that claimed to be single-protein diets had been contaminated by other proteins. The companies that produce the hydrolysed diets for this purpose ensure that their facilities are entirely cleaned down before the hydrolysed diet is made in order to ensure no contamination is present.

My pet has a food allergy – now what?

The good news is that once you’ve successfully diagnosed a food allergy in your pet, the treatment is simple – stop them eating the protein they react to. This usually means being very careful with their diet. If their allergen is a common ingredient, like beef or chicken, you’ll need to make sure that your vets, groomers and pet sitters are aware, so that they don’t inadvertently feed the allergen as a treat. From a vet’s point of view – please remind us regularly and especially before we give your dog or cat any treats! Notes like food allergies can get lost in the patient record and we’d hate to set them off. It’s also a good idea to check with us when you’re starting a medication for your pet. Many pet medications are now flavored to encourage your pet to accept them, but if this flavoring is natural it could cause a flare-up in your dog. 

Some dogs are allergic to pollen from weeds or trees as well as to their diet. If your pet isn’t 100% normal even on their new diet, talk to your vet about investigating an environmental allergy. You can read more about that in our articles about dog allergens {link} and cat allergens {link}.

Hill’s z/d for Dogs

Hill’s z/d is a dog food often used by vets in food diet trials. It contains hydrolysed proteins that are too small for your dog’s body to recognize them as a threat. 

Royal Canin Veterinary Diet Hydrolysed Protein

This hydrolysed diet from Royal Canin uses hydrolysed soy protein as the protein source so that your dog cannot react to it.

Food allergies in pets – The bottom line

Food allergies in pets are not as common as food company marketing would have you believe, but they do exist and they can impact on your pet’s quality of life. Getting to the bottom of what’s going on is a team effort between you and your veterinarian, but your pet will thank you for it!

Dr Joanna Woodnutt MRCVS

After graduating as a veterinarian from the University of Nottingham, Dr Joanna Woodnutt went on to practice companion animal medicine in the Midlands. She quickly developed a love of consulting and helping clients with medical problems such as dermatology, behaviour and nutrition - anything that involved helping clients understand their pets better. Jo started writing about pet health in 2017, realising that it meant she could help even more pet parents. Since then, she has written for countless online and print publications and is a regular contributor for Edition Dog Magazine. Jo now lives in the Channel Islands with her husband Ian and terrier Pixie, and they are expecting their first child very soon.