Grey cat sniffing its cat bowl

Cats that throw up undigested food are often just eating too quickly.

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My cat has adverse reactions to food

By Dr Hester Mulhall MA, VetMB, MRCVS Veterinarian

Updated on the

Getting to the bottom of your cat's adverse reaction to food is explored here.

If your cat has a bad reaction to food, from vomiting to skin complaints, it could be that your pet has a food allergy. If that's the case, you'll need to visit the vet to find the exact cause of this reaction and to determine what new diet to put your cat on.

What is the most common food allergy in cats?

It is often difficult to identify the exact dietary cause of a food allergy, and it is likely that a cat will be allergic to more than one ingredient. Common allergies are to ingredients that cats are more often exposed to including chicken, beef, seafood, egg, dairy and gluten.

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

This will vary between individuals and may include gastrointestinal symptoms such as vomiting and diarrhoea, as well as skin complaints such as itching and hair loss. It can be very difficult to ascertain whether a dietary allergy is the cause of these problems. Often the diagnostic process involves ruling out other common causes of the symptoms first, and then introducing a dietary trial to see whether the symptoms resolve on a different food. These trials need to be done in a very controlled way, and usually for a period of at least 12 weeks under veterinary guidance. This is likely to involve feeding a novel source of protein that your cat is unlikely to have eaten previously. An alternative is a hydrolysed diet, in which the protein has been broken down into smaller particles that are less likely to trigger an immune allergic response.

Can cats be allergic to wet food?

Yes. A cat can develop a food allergy to the ingredients in their food, regardless of whether it is wet or dry.

What do you feed a cat with a food allergy?

Speak to a vet first to find out what they advise. A hydrolysed diet can be suitable for some cats, but other cats are not keen on the taste of these and they tend to cost more due to the expensive production processes. A novel protein diet can also be a good option and will often contain a more unusual ingredient such as duck or venison with potatoes.

How long does it take a cat to recover from a food allergy?

This will vary between individuals, but it can take a period of some weeks for the reaction to resolve. Diet trials will often last for at least 12 weeks to reflect this, but it can take significantly longer.

What do you feed a cat with a food intolerance?

A food intolerance is technically different from a food allergy, although the terms are sometimes confused. The difference lies in the body’s reaction to the diet. With an allergy, the immune system is triggered inappropriately as a response to an allergen within the diet. But a food intolerance refers to an adverse reaction from the gastrointestinal tract that does not activate the immune system. This means that an intolerance may occur due to how a particular diet is cooked or prepared, and not just due to specific ingredients (although this is possible too). For example, some cats do better on a wet diet and others do better on a dry diet. Generally, a diet trial can help to identify a food that suits your cat, and this should not take as long to be effective as with a food allergy.

What is the best food for cats with sensitive stomachs?

If your cat has a sensitive stomach, there are some specially designed easy to digest diets that may be suitable. It is worth booking in an appointment with a vet first, to check for any underlying causes of their dietary sensitivities and for individual advice.

What do you feed cats with digestive problems?

This depends on the cause of the digestive problems. If your cat is experiencing a short episode of diarrhoea or vomiting, then you can feed them a sensitive diet for a few days while these resolve. Remember to reintroduce their usual diet gradually by mixing the two diets together for a few days and increasing the proportion of normal food. If the digestive problems are caused by a dietary allergy, then you may need to feed your cat a novel protein or hydrolysed diet.

What helps settle a cat's stomach?

Do not starve a cat with diarrhoea, as this can delay recovery, increase dehydration and lead to deficiencies in essential amino acids. If your cat has mild diarrhoea, they should be OK on their usual diet. Alternatively feed a specially designed sensitive diet, or cook a bland source of protein, such as boiled chicken breast or white fish (without oil or seasoning). If you speak to a vet, they may also advise the use of prebiotics, as there is some evidence that this can help to re-balance the gut microbiome.

Why is my cat throwing up undigested food?

A common cause of this is that they are eating too quickly. Using a puzzle feeder or feeding smaller meals more often may help with this. They may otherwise be intolerant to the food, and feeding a different diet for sensitive stomachs could help. Other causes can include stomach irritation due to hairballs, regurgitation (bringing the food up passively for some reason) or a gastrointestinal blockage. If your cat is showing other symptoms, or feeding a sensitive diet is not helping, then seek veterinary advice.

How do I get my cat to stop throwing up food?

This depends on the underlying cause, and an appointment with a vet will help to establish this. A diagnosis and treatment plan may include feeding smaller meals more regularly or trialling a novel diet. Your cat may also require diagnostic tests such as bloodwork or imaging.

How do I get my cat to stop throwing up after eating?

If your cat is throwing up soon after eating, this is often because they are eating too fast. If a puzzle feeder does not help with this, you can try feeding smaller meals throughout the day or giving them a sensitive food. If they are still bringing up their food after a meal, discuss with a vet whether a dietary trial might be appropriate.

Is it normal for a cat to throw up every day?

Even an otherwise healthy cat will vomit every now and then, which could be due to hairball irritation or an infectious agent. Yet it is not normal for this to be a frequent, regular occurrence. If your cat is vomiting on a daily basis, then they need a check-up with a vet to diagnose the underlying cause. There are many other causes of gastrointestinal symptoms, besides dietary allergies, and it is likely that your cat will need some diagnostic tests in addition to a thorough clinical examination.

When should I see a vet?

If your cat is showing signs of dietary allergy such as gastrointestinal or skin symptoms, then it is helpful to discuss these with a vet early on. This is so that other common causes of the symptoms can be investigated, and the vet can suggest the most appropriate controlled diet plan to suit your cat.

What should I ask a vet about the best diet for my cat with a bad reaction to food?

Book an appointment with a vet to discuss your cat’s symptoms and ask any questions you may have about diet. Take along any food packaging, including treats, so that the vet can see the ingredients. Even very high quality foods can cause food allergies, and it is likely that a special diet containing a new protein source will need to be trialled. The vet will be able to advise you where to start with this. Remember not to feed any additional treats or dietary supplements in addition to the new diet, as this is likely to affect the outcome.

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