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Food Allergy

Adverse reactions to substances within the diet, known as a food allergy, cause year-round itchy (pruritic) skin, with all the resultant signs that may entail.

Protein sources such as fish, chicken and dairy products are the most common to cause problems, but anything that your cat eats on a regular basis can become an allergen.

Remember that the body develops an allergic response after repeated exposure to an allergen common in their environment.

It is also worth remembering that most commercial foods contain fish and chicken additives, no matter what flavour is stated on the packaging, and so simply changing brands will not help.

Itchiness is non-seasonal, as your cat eats the allergen all year round, and the degree of itch can be mild to severe.

Itching generally leads to self-trauma, with licking, scratching and chewing leading to areas of hair loss, scabs and secondary infections with bacteria or yeasts. Recurring ear infections are commonly seen due to irritation leading to increased wax production within the ear canals and resultant infection.

It is important to note that many itchy cats will mainly lick as opposed to scratch, and a common clinical sign of pruritis is areas of hair loss from the forelegs, flanks or tummy. This is often symmetrical and well demarcated and sometimes confused for hormonal causes of hair loss.

A small percentage of animals may also develop gastrointestinal signs such as vomiting or diarrhoea.


The only accurate way to diagnose a food allergy is by a strictly controlled food trial

-      A novel protein, or proteins commercially broken down (hydrolysed) to an unrecognizable size are fed exclusively.

-      This is performed by either preparing a home-cooked diet containing a protein your cat has never eaten before and a specially chosen carbohydrate, such as rice, or by feeding a prescription hypoallergenic diet from Acorn. Getting your cat to eat a proper home cooked diet can be more difficult than with dogs, and hence prescription diets are generally recommended.

-      The food trial is continued for 8-10 weeks, with NO other foods given. No treats,snacks or milk should be given during this period.

Remember that even a single mouthful of an allergen can lead to a marked reaction, just as with a person with a peanut allergy, so strict adherence is VITAL for the trial to be diagnostic.

In cats with secondary infections and severe pruritis, we will generally treat these concurrently with the trial.

Clinical improvement is suggestive of the diagnosis, but to check, your cat should be challenged with the old diet. An immediate return of itching confirms food allergy.


Food allergy, once diagnosed, is easy to treat, by merely preventing the offending allergen from inclusion in the diet. Relapses in animals that steal the wrong foods are commonly seen.

If your cat can be convinced to eat the correct diet long term then prognosis is excellent.