Understanding Food Allergies and Intolerance in Cats

Which of the following are signs your cat could have a food allergy or intolerance?

a) Upset stomach

b) Dull coat

c) Itchy skin

[You’ll find the answer at the end of this article!]

Under estimated, overlooked, and under diagnosed: Pretty much sums up food allergy and food intolerance in the cat. This is a pity, because the effects are far reaching and yet once diagnosed, with the co-operation of the cat’s appetite (more of this later!) the patient can often be ‘cured’ of their symptoms.

But first, let’s break these problems down into bite-sized chunks.

One For All and All For One?

Are food allergy and food intolerance the same thing?

Actually, no, they aren’t. There are subtle differences between an allergy and intolerance.

Food Allergy

• Results from an overactive immune system which acts inappropriately when faced with certain food types. This is a similar idea to hay fever in people, with an allergic reaction to pollen.
• Food allergy tends to develop over time, as the immune response builds with each repeated exposure. This means a food the cat was initially fine with, when fed regularly could cause an allergic reaction.

Food Intolerance

• This is the inability to digest a certain food. The classic example is the cat that develops diarrhoea when they drink milk. This is the results of a lack of lactase, the enzyme necessary to break down the milk sugar, lactose.
• Food intolerance is often present from birth, and causes ill effects the first time the cat eats that food.

The implications of this are that a cat with a bad reaction to a food the first time they eat it, is likely to have food intolerance, whereas the cat that develops symptoms despite no recent change of diet may have a food allergy.

Signs and Symptoms

There are three main reasons food-related disorders go under diagnosed. These are:

• The symptoms are very general
• There is no lab test that accurately diagnoses the problem
• Getting a cat to eat a special elimination diet can be tricky

OK, let’s chew this problem over and digest the general nature of the symptoms. These tend to affect the digestive tract and /or the skin.

Gut-related Symptoms

• Sickness / vomiting
• Diarrhoea
• Colitis (soft stools with mucus and blood)
• Poor coat (due to poor absorption of vitamins)
• Weight loss (poor absorption of nutrients)

Skin-related Symptoms

• Itchiness, especially a non-seasonal itch
• Over grooming
• Symmetrical hair loss, most likely around the head and neck
• Miliary dermatitis (small, millet-sized scabs scattered over the skin)
• Rodent ulcers: Erosive, yellow-cream ulcers on the lips or mouth

Here we have a problem, because there are many reasons that a cat might be sick or have diarrhoea that are nothing to do with food allergy or intolerance. For example, a quick brainstorm of causes of stomach upsets goes something like this: Eating spoilt food, hairballs, worms, infection, pancreatitis, cancer…you get the picture!

Likewise, the itchy cat might have a simple common problem such as flea allergy dermatitis or be hosting mites that make her itchy. She may even be stressed and licks herself as a comfort strategy, in the same way a child sucks their thumb.

So given the general natural of food allergy and intolerance, how is the problem diagnosed?

Diagnosing Food-Related Disorders

Remember we said there was no lab test that can accurately diagnose food allergy or intolerance? This poses a problem.

Given the general nature of the signs there’s nothing for it but to rule out all other problems first, and if the results are normal or negative, consider a dietary trial. Indeed, for the co-operative cat that is otherwise well, the vet may suggest an ‘elimination’ diet to run in parallel with those other tests.

Thus, the vet may run faecal tests (screening for parasites and infection), blood tests (checking organ function), bowel function tests (looking at the balance of digestive enzymes and vitamins in the gut), ultrasound (looking for signs of cancer), and possibly even bowel biopsies.

If there’s a strong suspicion early on that food is the culprit then the vet may deworm the patient, make sure they have good parasite control in place, and then suggest an elimination diet.

The Details of an Elimination Diet

If your head hurts because you keep banging it against a brick wall, the answer is not painkillers but to stop knocking your head. In the same way, food-related disorders settle down once the offending food is removed.

An elimination diet means feeding a tightly restricted diet, often consisting of a single protein and carbohydrate that the cat has never eaten before. The idea is that removal of the offending food stuff allows the symptoms to settle. In short, if the cat improves on the special diet then food intolerance or allergy is highly likely.

Sounds easy! However, there are drawbacks. Number one is the cat herself. Many cats are fussy eaters, and being offered a new food and being expected to eat it rarely goes down well. Secondly, the cat must eat that diet and absolutely nothing else, which can be tricky. Thirdly, it can take eight weeks of a strictly controlled elimination diet before improvements start to be seen.

Put like that, it doesn’t sound quite so easy, does it?

Treatment of Dietary Allergies or Intolerance

For those in the happy position that the cat chows down on the restricted diet, there is every chance of a full resolution of symptoms. The choice is then either to keep feeding that diet, or slowly reintroducing one new food every two weeks, monitoring carefully for signs of ill health. If the new food generates symptoms, it’s removed from the menu.

However, for many cats a compromise is reached. They avoid the offending foods as much as possible, but medical treatment may be necessary to suppress the worst of the signs.

These treatments include:

• Steroids: These are potent anti-inflammatory drugs which help to reduce swelling of the bowel wall that result from food allergy
• Antibiotics: Such as metronidazole, which has a dual action of killing some unwanted bowel colonizers and having an anti-inflammatory action
• Immunosuppressive medications: Such as chlorambucil, work by supressing the immune system and down-regulating the exaggerated response.

And finally, remember the question posed at the beginning of this post. . .  here’s the answer.

Answer: Well done if you answered “All of them: a, b, and c” because as you know now, dietary related disorders can affect the gut, skin, and general well-being.