How Can I Tell if My Pet is Allergic to Food?

Royal Canin Anallergenic is available as dry food for a cat or dog

After eating, your cat or dog has vomiting and diarrhoea. This might be combined with frantic overgrooming, biting skin, inflamed skin and scratching at itchy skin. This happened to Tabitha and a hypoallergenic diet stopped the symptoms, so I wanted to write about her new dry food diet that stopped the above symptoms. Royal Canin formulated a nutritionally complete dry biscuit diet that excludes allergens that trigger the signs of allergies or intolerances.

Pet food sold in supermarket brands is of low nutritional content.

Is this why?

  • Bulked with grains and starches. Cats are unable to digest in large amounts
  • By-products (often top of the ingredient list as ‘meat’) is often from fishing processing plants and slaughterhouses humans cannot eat.
  • Foods are cooked at high temperatures (which destroys nutrients) and dehydrating the by-product until powder is added to dry food
  • Hidden ingredients so if your cat has a sickness, then it is difficult to deter what ingredient is the cause

Pet food is mass-produced. Supermarket pet food is more affordable but the processes will differ when compared to a brand that follows the correct processing of grains, wheat and corn to create food that offers health benefits to your pet. I doubt the cheaper brands were blended to produce foods that will help a cat or dog with an allergy.

If your pet is showing the signs mentioned previously, please consult with your vet. Your veterinary surgeon may want to perform other tests on your cat. These can be costly. Tabitha’s health improved when I bought Royal Canin Anallergenic and Hypoallergenic dry kibble because it was a specifically designed food with removed ingredients causing issues.

Royal Canin say:

Veterinary science and careful observation to identify the most suitable nutrients‘ in its complete dog or cat food.

Royal Canin

What is Royal Canin’s verdict for their products?

  • Only dehydrated meat meal and by-products are used if fit for human consumption. They state that if correctly processed, these provide an excellent source of protein. Livers, hearts and lungs are beneficial to your pet for nutrition and Royal Canin lists these as animal derivatives on its product ingredient list. As for dehydrating the meat, it removes excess water and fat. This results in more protein which in turn may contain useful vitamins and minerals required for optimal pet health
  • I never knew wheat gluten is a digestible source of protein for both cats and dogs
  • They report that grains are very nutritious and digestible if the outer husk is removed and if they are properly processed. Grains include rye, oats, millet, wheat, and rice and give your cat and dog energy. Other beneficial reasons why grain is excellent for your pet are magnesium, complex carbohydrates, fibre and iron it provides. And surprisingly, other grains give our pets healthy protein, essential amino acids and omega three fatty acids
  • As well as supporting energy, rice is easy to digest and supports gastrointestinal
  • Corn kernels are nutritious and, if correctly processed, will be digestible and contain healthy protein, fatty acids and fibre. Like wheat, it contains gluten. Overall, corn is beneficial because it also provides amino acids to support bladder health and skin, includes antioxidants and various vitamins

Royal Canin Veterinary Anallergenic dry biscuits are designed to exclude sources of food allergens, which is great news for our felines and canines. Royal Canin can be expensive but it is good quality food and meets a cat or dog’s nutritional requirements. From experience of giving my pets renal, fibre response and gastrointestinal, the product does what it promises. This is why I buy Royal Canin pet food instead of supermarket brands.

Health benefits are great but your pet may be allergic to grain, eggs or any particular ingredient. My sister’s dog frantically scratched because at his skin because of the grain content.

Tabitha’s symptoms:

Tabitha is a geriatric La Perm.

  • Diarrhoea and vomiting
  • Weight decreased to under 3kg
  • Frantic overgrooming of unmatted fur
  • My vet mentioned euthanasia three times because of her low weight
  • Euthanasia voiced again because she would not eat during her veterinary stay (Tabitha ate heartedly when home)
  • Various tests to include cancer. Total veterinary bill: £1500
  • Tabitha did not have tests for allergies

The diagnosis was cystitis and food allergies. It was recommended I feed her on Hypoallergenic and Anallergenic food. The diarrhoea and vomiting stopped, and her fur grew back. For cystitis, the vet suggested regular urine tests to keep a check on cystitis. Because Tabitha is timid, they recommended I take a urine sample at home and bring it to the practice for testing. Feline Cystease cost me more than £6 each but today (March 2022) it costs £7.99.

Tabitha gives a paw up!Tabitha gives a paw down …
Tabitha thinks they are delicious and loves eating themKeeps sealed as the biscuits soften
The biggest weight you can buy is 4kgNot cost-effective to buy a 1kg bag
Buy from online vet stores as cheaperTabitha is on a Pet Health Care plan with 50% off cat food. Her vet now does not stock Royal Canin
The diarrhoea and vomiting stopped in days!More expensive at big pet supermarkets (Pets st Home, Jollyes etc)

What are the signs of a dog or cat having an intolerant or allergy towards certain foods?

If your cat or dog is vomiting or having diarrhoea soon after eating, the food they are eating may be the culprit. When vomiting, it would be food eaten and not regurgitate after a cat eats grass.

The other signs are biting, licking and scratching at body parts. Are there signs of inflammation?

As well as vomiting and diarrhoea, Tabitha pulled out half her body fur. I thought this was stress, but it is possible because she suffered skin irritation, food allergy, or intolerance, and she pulled her fur out. I wish my vet had suggested this food before they ran £1500 of tests and hospital stay, but they needed to rule out any other problems first. Not forgetting the repeated suggestions she may need to be euthanised. After the tests, they suggested hypoallergenic and Anallergenic food. This happened in October 2020.

Royal Canin recommends you seek your vet’s advice before you feed your cat or dog this product. My vet recommended both Anallergenic and hypoallergenic. However, it is available to buy freely online if you want to buy it without speaking to your vet.

I want to point out the following:

Molly had renal problems and her vet at the time recommended renal food. I bought Royal Canin. I remember asking the vet if Tabitha would eat it even though she did not have kidney problems. He said yes, but looking back may have assumed I meant occasional small amounts. I meant to give her renal food as her complete diet. When Tabitha had her regular Old Cat blood check-up for thyroid and kidney, I was told she had issues (maybe protein levels were low but I cannot remember). He asked what her diet was. Eating daily renal dry biscuits caused this.

With Molly, she was picked up as a stray aged 15 (believed dumped) and her protein levels were low because she wasn’t getting the right food outdoors to maintain protein levels.

So my point is – maybe check with your vet first.

Can I buy Anallergenic without a veterinary prescription?

You do not require a prescription to buy this food. You cannot purchase this brand in well-known supermarkets such as Asda, Tesco or Sainsburys. But you can buy Royal Canin in the big warehouse pet stores such as Pets at Home or Jollyes. However, they make stock of the brand but not the type.

You will find Royal Canin cheaper from an online pet store, and the carriage costs may be zero depending on the bag size you purchase.

Below are my recommended list of online stores. Prices vary, so please visit each to check the costs and carriage. Also, Zooplus tends to have discount offers every few weeks. Animeddirect I stopped using as they had despatch issues during the pandemic.

What are the benefits of Royal Canin Anallergenic?

Royal Canin anallergenic are small in size and suitable for a geriatric cat without teeth
Anallergenic are small in size

The following is taken from the bag of Royal Canin Anallergenic I buy regularly.

Antioxidant Complex – A synergistic complex of antioxidants to help neutralise free radicals
Skin Barrier – Formulated to support the skin’s natural protective barrier for optimal skin health
Allergen Restriction – Formula and production process aimed at excluding sources of food allergen
Oligopeptides – Low molecular weight peptides to reduce the risk of nutrient intolerance

Tabitha’s diarrhoea, vomiting and fur pulling ceased within days of starting a Royal Canin Anallergenic and Royal Canin Hypoallergenic diet.

How much do I feed my cat or dog?

Royal Canin put a chart on the reverse of the bag. Of course, you need to know your pet’s weight.

Here is an example for a cat, according to Royal Canin.

in Kg
Thin weight
Normal weight
If feeding your cat or dog a dry diet, give plenty of water for hydration

Do I feed my pet anallergenic for a certain period of time?

First of all, whatever your vet suggests will override this article.

At the back of the bag of biscuits, Royal Canin writes that you should feed your cat or dog Anallergenic food for 3 to 8 weeks. Then suggests continuing this diet if the signs of intolerance disappear. You must seek veterinary advice if your dog or cat still has an upset tummy.

Diarrhoea and vomiting stopped with Tabitha, and I continued giving her the biscuits. She has Royal Canin Hypoallergenic and Purina Hypoallergenic too, but Anallergenic is a firm favourite. Tabitha will refuse to eat the alternatives if she knows Anallergenic is available.

Is the biscuit the right size for an elderly cat or dog without many teeth?

Cats dogs with food allergies.  Small dry biscuits for old cats and dogs
Royal Canin Anallergenic biscuits are small in size

I have only ever bought cat biscuits. Tabitha is 15 and has about three teeth left. According to her vet, eating dry food with very teeth will not hurt her mouth in any way.

Hopefully, the photograph above will give you an idea of the width. The depth is very minimal.

Is sensitive dry or wet food the same type of product?

I asked my vet about this, and she said no. Hypoallergenic and Anallergenic are formulated for pets suffering from allergies and intolerances.

Is Anallergenic available as wet food?

Sadly no. Royal Canin told me to mix the dry biscuits with a little water to soften them. Do not serve hot!

Tabitha did not like her biscuits served this way.

If you keep the bag sealed, the biscuits remain hard. If you allow air to get it, it softens them. Tabitha eats them regardless.

Is there an alternative wet food for my cat or dog?

I recently ordered a Taster Box from Republic of Cats. The offer price is now £10.00 (December 2022) and includes 15 cans of wet food and a 0.45kg bag of kibble. 28 meals aren’t bad!

I selected wet and dry food without rice, dairy, barley, eggs, oats and wheat. You can cancel at any time or delay future orders.

I recommend trying the food if your cat or kitten has allergies. It helps the finances and you can cancel anytime. Here is my referral link if you want to read more or order the taster box. As a referral, Tabitha gets a discount on her next box of yummy food!


I am not a veterinary professional. This article does not give medical advice. If you have any concerns about your pet, I urge you to seek advice from a qualified veterinary surgeon in the first instance. 

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The reason I write and make YouTube videos is to help you and your pets from my experiences, and to take you through a journey of Green Living from worm composting and bokashi.