Scottish Fold cat looking at food bowl

Cats are commonly allergic to the most frequently used foods.

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Is my cat allergic to their food?

By Dr. Liz Barton MA, VetMB, MRCVS Veterinarian

Updated on the

If you cat suddenly has skin allergies and a bad tummy, they could be allergic to their food.

An owner may think their cat is allergic to their food, if they see signs such as skin reactions or diarrhoea and vomiting. But it won't be at all clear that the cat is reacting to food specifically until the cat's diet is changed. Here you'll find information on how to do just that and how to help your feline with problems such as itchy skin allergies in the meantime.

What can I feed my cat with skin allergies?

There are many components in the diet that can help with skin health. Even if your cat has allergies to things other than food that are causing a skin reaction, feeding a skin or ‘dermatology’ diet can help. Most diets for allergic cats are hypoallergenic, so contain novel proteins and carbohydrates that are easily digestible and less likely to cause an immune response. Essential fatty acids also help to support skin health and reduce immune reaction. Antioxidants may also be added to reduce damage caused by free radicals.

How can I treat my cat's skin allergies?

The best way to treat an allergy is to avoid the cause. If this is not possible through a change in diet or environment, then treatment to reduce the immune response may be needed. This often includes antihistamines, steroids or other immune-modulating prescription medications. For small patches of allergy, creams or washes may be recommended. Generally, full baths are not recommended for cats, because even though they may be effective treatment, they are too stressful for both cat and owner. Secondary infections may also need treating with antibiotics. Supplements such as probiotics, essential fatty acids and antioxidants can help to reduce the allergic response and improve skin health.

How can I tell if my cat is allergic to their food?

Cats allergic to food may have gut symptoms, including diarrhoea and vomiting. Alternatively, they may show skin reactions that may be associated with the face and around the bottom, or can be more generalised over the body. These are typically a result of overgrooming due to itchiness of the skin, leading to hair loss, reddening, scabs and sores. Allergies are most common in middle-aged cats, which is when they are 4 to 5 years old.

The only way to prove the food is causing the allergic reaction is to swap to a completely novel source of protein and carbohydrate only for a full 12 weeks. If the allergy settles, then food is likely to be part of the problem (your cat may be allergic to more than one thing, such as food and fleas). The only way to prove it absolutely would be to feed your cat the previous food and if it causes an allergic response then you can be sure that was the cause.

What causes cat skin allergies?

Your cat’s immune response is responsible for allergies. It is an over-reaction of the body to certain proteins and glycoproteins that are ingested, inhaled or contacted. A normal immune response should just ‘ignore’ these allergens, but in allergic cats the immunity becomes sensitised and starts reacting to substances it should just ignore. This is commonly allergens that your cat has tolerated fine for years, such as chicken or beef protein. Often these errant immune responses occur when they are approaching middle age at 4-5 years old.

What are the most common food allergies in cats?

The old phrase, ‘common things are common’ applies to cat food allergies. They are most commonly allergic to the most frequently used foods, including beef, chicken, seafood, egg, dairy and gluten. Cats aren’t designed to eat carbohydrates, so diets containing high levels of cereal ‘fillers’ are not good for cats. The majority of their diet should be protein and fat.

How long does it take for food allergies to go away in cats?

Once the immune system starts reacting to food, it is unlikely to desensitise again. If you remove the food allergy, it still takes several weeks for the skin to settle and the allergic response to settle. Certain treatments may be needed to help your cat and to reduce the irritating itch while this happens.

What do you feed a cat with food allergies?

Cats with food allergies can be fed novel protein and carbohydrate as a ‘hypoallergenic’ diet. Hydrolysed diets are broken down into very small proteins, so are less likely to cause any immune response. The addition of essential fatty acids and antioxidants in these diets can help to calm the immune response and keep skin healthy.

Can cats be allergic to wet food?

Cats can be allergic to wet food or dry food. It all comes down to the allergens that your cat is allergic to, which can be present in all types of food.

When should I see a vet?

If your cat has sores on their body or hair loss, it’s important to see a vet quickly. Feeling constantly itchy is not great for their welfare, and it’s best treated early before secondary bacterial infections take hold. The commonest cause of skin disease is fleas, so if you’re sure your cat doesn’t have fleas – or if you’ve treated them but can still see live fleas – then it’s best to see a vet.

What should I ask a vet about cat nutrition and allergies?

Only 1 to 11 per cent of cats with skin disease will have a food allergy, so this may not be the first thing discussed when you visit a vet. They may advise ruling out parasites and giving a short course of treatment, then discuss food allergies, if the problem becomes persistent or recurrent for your cat. You should update them on what you have fed your cat, now and in the past, with as much detail of additional treats etc. as you can. They can then discuss the best diet to trial, how long for and any additional food supplements recommended to keep your cat’s skin healthy.

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