Allergies is one of the health conditions that cats owners should know about, because it affects quality of life, and it is easier to manage when it is caught early. This guide explains what allergies is, the signs to watch for, what causes it, how it is diagnosed, how it is treated, whether it can be prevented, and how to live with a cat that has it. Every suggestion here is general guidance, not a prescription for an individual cat.

This guide covers allergies in cats in full: what it is, the signs to watch for, what causes it, how it is diagnosed, how it is treated, whether it can be prevented, and how to live with a cat that has it. Every suggestion here is general guidance, not a prescription for an individual cat, and a cat with allergies should be checked by a vet, because the right treatment depends on the individual cat, its age, and how advanced the condition is.

What is allergies in cats?

Allergies are a condition where the immune system overreacts to something that is harmless to most cats — a food, a pollen, a flea bite, or something in the environment. The most common signs are itching and skin problems, but allergies can also cause ear infections and stomach trouble. Allergies are common in cats, and they are a long-term condition: they can be managed, but they rarely go away on their own, and a cat with allergies will usually need lifelong care.

The rest of this guide covers the signs, the causes, how allergies is diagnosed, how it is treated, whether it can be prevented, and how to live with a cat that has it. A cat with allergies should be checked by a vet, because the right treatment depends on the individual cat, its age, and how advanced the condition is — and because some of the signs of allergies can also be signs of other conditions, which need a vet to tell apart. The cat ideal weight calculator works out a target weight range, and the when is a cat considered a senior guide gives the senior thresholds by size.

Signs of allergies in cats

The signs of allergies in cats are listed below. Not every cat with allergies will show every sign, and some cats will show only one or two — but any one of these signs, especially if it lasts more than a few days or gets worse, is worth mentioning to a vet. A cat that is bright, eating, drinking, and otherwise well between episodes is less likely to be seriously ill than a cat that is lethargic, off its food, or losing weight — but the only way to know is to check.

  • Itching, scratching, licking, or chewing at the skin, especially the paws, ears, and belly.
  • Red, sore, or inflamed skin, and hot spots where the cat has scratched.
  • Ear infections that keep coming back, with head shaking and a smell.
  • Hair loss, and a dull or patchy coat.
  • Stomach trouble — vomiting, loose stools, or gas — after eating.
  • Sneezing, a runny nose, or watery eyes, in some cats.
  • A cat that is restless, uncomfortable, or not sleeping well because of itching.

If two or more of those signs apply, or if one sign is severe — a cat that cannot urinate, cannot breathe, cannot stand, or has had a seizure lasting more than five minutes — see a vet the same day. Those are signs that need a vet, not waiting. Bring a note of when the signs started, how often they happen, and what the cat eats and drinks — that information helps the vet far more than a guess about the cause. The how to tell if your cat is overweight guide gives the hands-on check for weight, which matters for many of these conditions.

Causes and risk factors for allergies

Allergies are caused by the immune system overreacting to a trigger. The most common triggers are fleas, food, and things in the environment — pollens, dust mites, and moulds. A food allergy is usually to a protein, such as chicken or beef, and it is different from a food intolerance, which upsets the gut without involving the immune system. Some cats are more prone to allergies than others, because of their genes, and allergies often start in young adults and get worse over time if the trigger is not found.

Some cats are more prone to allergies than others, because of their genes, their breed, their size, or their age — but breed and age are not destiny, and a cat of any breed can develop allergies. What an owner can control is weight, food, exercise, and vet checks: a cat at a healthy weight, with measured food and daily exercise, is less likely to develop allergies and will cope better with it if it does. A cat that is overweight, that eats a poor diet, or that never sees a vet is more likely to develop allergies and to have it found late, when it is harder to treat.

How allergies is diagnosed

A vet diagnoses allergies by ruling out other causes first — parasites, infections, and other skin problems — and then by testing for the trigger. For a food allergy, the usual test is an elimination diet: a food with a protein the cat has never eaten before, fed exclusively for six to eight weeks, with the vet's guidance. For environmental allergies, the vet may do a skin test or a blood test. Finding the trigger takes time, and it often takes several visits — but it is worth doing, because avoiding the trigger is the best treatment there is.

If you are worried about your cat, see a vet and mention allergies by name, with the signs you have seen and when they started. Bring a note of what the cat eats, how much, and any medicines it takes, and whether it has had allergies or a related condition before. A video of the signs, if it is safe to take one, helps the vet far more than a description — especially for seizures, limping, or breathing problems. Do not try to diagnose allergies yourself, and do not buy medicines or special diets for it without veterinary advice, because the wrong treatment can make it worse.

Treatment and management of allergies

Treatment is about avoiding the trigger and controlling the itch. If the trigger is a food, the cat must eat a food without it, for life. If the trigger is fleas, strict flea control for the cat and the house is essential. If the trigger is in the environment, it may be harder to avoid, and the vet may prescribe medicines to control the itch and the inflammation, or a course of injections to desensitise the cat to the trigger. Do not give medicines meant for people without veterinary advice, and do not try an elimination diet without the vet's guidance — a home-made elimination diet is often unbalanced.

Treatment is a decision made with the vet, weighing the cat's age, health, and quality of life against the treatment and its side effects. Some owners choose not to treat, and to keep the cat comfortable instead — and that is a valid choice, made with the vet, not on the basis of a web page. Whatever is decided, the treatment must be followed every day, at the same times, and the cat must be checked regularly, because allergies changes over time, and the treatment needs to change with it. Do not stop a medicine suddenly, and do not change the dose without veterinary advice.

Living with a cat with allergies

A cat with allergies can live a full and happy life with the right care, but it needs a routine: the right food, strict flea control, regular baths or skin care as the vet advises, and medicines when they are needed. The owner must watch for flare-ups — more itching, more ear infections, more stomach trouble — and mention them to the vet promptly, because a flare-up caught early is easier to treat than one left for weeks. Keep a note of what the cat eats and when it itches, because the pattern often shows the trigger.

Keep a routine: the same times for food, medicines, walks, and play, the same places for furniture, food, and water, and a calm, predictable home. Keep a note of appetite, drinking, weight, and behaviour, and mention any change to the vet promptly — a change that lasts more than a few days, or that gets worse, is worth a vet visit. Keep the cat at a healthy weight, with measured food and daily exercise at a level that suits its body, and keep vet checks regular: once a year as an adult, and twice a year as a senior. The senior cat diet guide covers feeding older cats, and the cat calorie calculator works out daily calories for any weight.

Can allergies be prevented?

Allergies cannot always be prevented, because much of them is about genes — but the risk can be reduced. Keep flea control up to date, because flea allergy is the most common allergy in cats and the easiest to prevent. Feed a simple, complete and balanced food, and do not change foods often or give a different treat every day, because every new ingredient is a new thing the gut has to cope with. If you are buying a kitten of a breed that is prone to allergies, ask what the parents were like, and be ready for a cat that may need lifelong care.

Early checks matter most: have the cat checked regularly, so allergies is found early, when treatment works best. Keep the cat at a healthy weight, with measured food and daily exercise, and mention any change in drinking, eating, weight, or behaviour to your vet early, because a change caught early is easier to treat than one left for weeks.

For related reading, see the cat ideal weight calculator, the cat body condition score chart, the how to tell if your cat is overweight guide, the senior cat diet guide, the cat calorie calculator, the when is a cat considered a senior guide.

Frequently asked questions

What is allergies in cats?

Allergies are a condition where the immune system overreacts to something that is harmless to most cats — a food, a pollen, a flea bite, or something in the environment. The most common signs are itching and skin problems, but allergies can also cause ear infections and stomach trouble. Allergies are common in cats, and they are a long-term condition: they can be managed, but they rarely go away on their own, and a cat with allergies will usually need lifelong care.

What are the signs of allergies in cats?

The most common signs are: Itching, scratching, licking, or chewing at the skin, especially the paws, ears, and belly. Red, sore, or inflamed skin, and hot spots where the cat has scratched. Ear infections that keep coming back, with head shaking and a smell. See the full list above for every sign to watch for, and see a vet promptly if two or more apply, or if one sign is severe.

What causes allergies in cats?

Allergies are caused by the immune system overreacting to a trigger. The most common triggers are fleas, food, and things in the environment — pollens, dust mites, and moulds. A food allergy is usually to a protein, such as chicken or beef, and it is different from a food intolerance, which upsets the gut without involving the immune system. Some cats are more prone to allergies than others, because of their genes, and allergies often start in young adults and get worse over time if the trigger is not found.

How is allergies diagnosed?

A vet diagnoses allergies by ruling out other causes first — parasites, infections, and other skin problems — and then by testing for the trigger. For a food allergy, the usual test is an elimination diet: a food with a protein the cat has never eaten before, fed exclusively for six to eight weeks, with the vet's guidance. For environmental allergies, the vet may do a skin test or a blood test. Finding the trigger takes time, and it often takes several visits — but it is worth doing, because avoiding the trigger is the best treatment there is.

How is allergies treated?

Treatment is about avoiding the trigger and controlling the itch. If the trigger is a food, the cat must eat a food without it, for life. If the trigger is fleas, strict flea control for the cat and the house is essential. If the trigger is in the environment, it may be harder to avoid, and the vet may prescribe medicines to control the itch and the inflammation, or a course of injections to desensitise the cat to the trigger. Do not give medicines meant for people without veterinary advice, and do not try an elimination diet without the vet's guidance — a home-made elimination diet is often unbalanced.

When should a cat with allergies see a vet?

See a vet promptly if the cat shows any of the signs above, especially if they last more than a few days or get worse — and the same day if the cat cannot urinate, cannot breathe, cannot stand, has had a seizure lasting more than five minutes, or is lethargic or off its food. Bring a note of when the signs started and what the cat eats and drinks. A cat with allergies should be checked by a vet, because the right treatment depends on the individual cat, its age, and how advanced the condition is.

Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.