What are cat food allergies?

Long shelves with cat foods and treats line every pet shop you step into. Online pet shops are the same, with their biggest and most varied offer being for pet foods and treats. And it’s normal to be so. We’re a nurturing species and we enjoy feeding our loved ones, be they two or four-legged. But sometimes food can cause problems too, as is the case of food allergies.

What are food allergies?

Food allergy is a type of hypersensitivity that cats can develop. This means that the cat’s gut immunity wrongly takes food proteins for harmful pathogens and starts producing antibodies against them, triggering a cascade of damaging effects.

Sometimes food allergies are grouped together with food intolerances under the umbrella term of Adverse Food Reactions (AFR) or Cutaneous Adverse Food Reactions (CAFR) because both are triggered by food and their symptoms are very similar. But there are a few notable differences between these two.

Food intolerances produce inflammation in the gut without antibody production, somewhat similar to human IBS. The symptoms appear from the very first time that the cat has the offending ingredient(s). These can also be very variable - proteins, carbohydrates, fats, various food colourants or additives or components that form during processing. Therefore the quality of food plays a role in intolerances. Intolerance symptoms appear quickly, but also resolve rapidly when the food is not fed anymore.

Food allergies involve the immune system, which produces allergen-specific antibodies. They develop slower in time, when your cat has had the same food for a long period of time. Sometimes it may take over 1 year before they manifest. The symptoms due to an allergy then also take longer to fade after the allergenic food is stopped. The quality of food ingredients plays almost no role here. That is, a cat allergic to chicken will be equally allergic to chicken from intensive farming or the most naturally and organically reared birds.

Needless to say, a food allergy can be triggered not only by cat food, the allergens could be in anything your cat eats, including treats and anything hunted outdoors.

The ingredients cats are most often allergic to are:

• beef,

• fish,

• chicken.

Some proteins show cross-reactivity if their structures are alike, meaning that a cat allergic to chicken could have symptoms after eating turkey (but they won’t necessarily be allergic to eggs).

The vast majority of cases involve proteins of animal origin, gluten (a wheat protein) allergies are virtually unknown in cats.

Cats can be allergic to casein (the main protein in dairy), but they shouldn’t be given milk because they, as a species, have a severe lactose (a natural milk sugar) intolerance. Hence the special ‘cat milk’ available in stores.

It’s not entirely clear why some animals develop food allergies and others don’t. A genetic predisposition to immune system reactivity is a possibility supported by the fact that many pets have two or more allergies at the same time. There’s some indication that in cats certain intestinal parasites like Toxocara cati make food allergies more likely or worse.

Most cats with food allergy are around 4-5 years old, both sexes being affected equally. Siamese cats seem to have a higher than average number of cases.

How to recognise if your cat has a food allergy?

Food-allergic cats may start with very mild symptoms that go either unrecognised or attributed to something else for a while. At some point, either because the concentration of antibodies has gotten high enough or a combination with other factors (stress, other illness, etc) they will have a severe reaction and end up at the vet.

An allergic flare-up usually starts with an itch that can become very severe as the time passes.

Later you might see:

• skin redness, spots, weepy or crusty areas,

• patches of thinning coat or even complete baldness,

• thickening and darkening of the skin.

Some cats also get:

• sores on the lips or on the body,

• frequent ear infections.

Cats can also develop abdominal signs like vomiting and diarrhoea or even respiratory signs like sneezing.

When to see your vet

If you suspect your cat may have a food allergy, it’s recommended to speak to a vet as soon as possible.

Allergies of any kind do not go away by themselves. The produced antibodies can vary in concentrations giving milder or worse symptoms (allergic flare-ups).

But overall these flare-ups only tend to get worse and happen at shorter and shorter intervals if measures are not taken to reduce or eliminate the immune reaction they cause.

What will the vet do? Diagnosis and treatment of food allergies

If your cat has bad skin symptoms, your vet will start with medication to treat these first, for example:

• antipruritics to reduce the itching (rarely steroids as these don’t work that well for food allergy-related itching),

• antibiotics to control secondary infections,

• anti-inflammatories to help with the skin irritation.

A thorough medical history of your cat will be taken to determine if a food allergy is their most likely allergy type (25 % of cats with a food allergy are atopic as well). This will be more likely if your pet:

• has an effective external parasites control, especially against fleas, so flea allergy dermatitis can be ruled out,

• shows symptoms that don’t vary at different times of the year,

• develops frequent gastrointestinal symptoms as well.

Blood tests for food allergies measuring antibodies against food proteins exist, but they have been found unreliable and are rarely used in practice. Same goes for the intradermal testing.

The most reliable way to diagnose food allergies in cats is to do an elimination diet food trial and find what they are and are not allergic to.

Food allergies are not the easiest to diagnose, but they are the easiest allergies to manage - it’s much simpler to control what your cat eats than what they come in contact with (like pollen or fleas).

Unfortunately, there is no treatment for food allergies yet, no way to teach gut immunity not to react to harmless foods. For unclear reasons, the itchiness caused by food allergies doesn’t respond very well to medication, as is the case of atopy. Finding foods that the cat is not allergic to and feeding them exclusively is the only possible way of preventing flare-ups.

How can you help your pet with a food allergy?

Feed your allergic cat only safe foods and treats that you know do not trigger allergic flare-ups. Cats obviously don't know which foods are not ok for them, so supervise closely what your cat eats and keep a diary of your pet’s foods, treats and symptoms so that you can share this information with your vet.

Occasional flare-ups may still happen - a well-intended neighbour will feed your cat a free dinner or they may eat something hunted. Note the places where symptoms start first (some cats will have red ears first, some itchy paws) so you can spot a flare-up early on.

Always speak to your vet or vet nurse when you are introducing new brands of foods or treats to your allergic cat. Pet food sold as ‘hypoallergenic’ is not always hydrolysed food, and most often refers to a novel protein or a limited ingredients type of food. Check the package carefully for the word ‘hydrolysed’, either on the front or in the list of ingredients. As mentioned above, gluten or grain-free diets are rarely useful for cats with food allergies since this allergen has a very small importance for cat food allergies.

Keep a soothing, skin barrier supporting mousse in your first-aid kit that you can use to calm their itchiness.

Last but not least, use the button on this page to give us a call whenever you have any questions about your food-allergic cat. Our vets will be happy to help you with any necessary advice and further insights!