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Food hypersensitivities and cutaneous adverse food reactions account for about 1-15% of all skin allergies seen in cats and are the third most common cause of feline allergy. It is thought that these cats are reacting to specific dietary proteins contained in their food. The most common dietary proteins implicated in causing food hypersensitivity in cats include beef, dairy products/milk, fish, lamb/mutton, chicken and gluten. Less commonly, reactions have also been observed towards pork, rabbit, horse and eggs. Many of these cats will also have concurrent flea allergy dermatitis and/or atopy so a thorough dermatological work up including implementation of a regimented flea control program is essential. The only way to definitively diagnosis a food hypersensitivity in cats is with a food elimination diet.

Symptoms of food hypersensitivity

Common symptoms of food hypersensitivity in cats are similar as those seen in other forms of allergy however the symptoms are not seasonal and persist year round.

• Obvious scratching, itching and self-induced skin trauma often around the ears and head.
• Facial dermatitis, may also involve the eyelids and ears. 40-50% of cases have lesions limited to the head, neck and ears.
• Symmetrical hair loss, often on the flanks or underbelly.
• “Miliary dermatitis”. This is characterised by tiny little crusts and sores over the body.
• Eosinophilic granuloma complex. This includes a number of types of lesions including indolent ulcers, eosinophilic plaques and eosinophilic granulomas.
• Some cats will have more than one symptom.
• Secondary bacterial and yeast infections are common.
• Some cats may show gastrointestinal signs.

Diagnosis

Diagnosis of food hypersensitivity involves firstly ruling out other potential causes of the symptoms via a complete and thorough dermatological work up. This involves obtaining a detailed history and performing a thorough physical examination before commencing laboratory testing. Recommended tests will likely include a number of skin tests such as skin scrapings, surface cytology, hair pluck examination and fungal cultures. For cats over the age of seven years, blood and urine tests will also need to be performed to include a complete blood count, chemistry panel, thyroid hormone testing and urinalysis. All these tests can be run at our hospital meaning you receive your cat’s results quickly. Please refer to our information sheet on Itchy Skin Disease for a more detailed explanation on the recommended approach.

After the initial round of testing if your vet has a high index of suspicion that your cat has a food hypersensitivity, they will recommend to feed an elimination diet in order to aid the diagnosis. An elimination diet is the only way to diagnosis food hypersensitivity in cats, as both serological blood testing and intradermal skin testing are very unreliable and not recommended.

Elimination Diets

The ideal diet to feed your cat for an elimination diet is one that will fail to elicit an allergic response. There are two options available:

• Novel (new) single protein source and single carbohydrate source that your cat has never eaten before (home cooked).
• Commercial hydrolysed veterinary prescription diets, the proteins in these diets are “hydrolysed” which breaks them down into tiny fragments that are too small to elicit allergic response.

Regardless of which option you decide to go with, it is important to introduce the new food to your cat very gradually over 1-2 weeks to increase palatability. The elimination diet will not commence until you have managed to get your cat eating 100% of the special diet. Once your cat is purely on the elimination diet, continue the trial for a minimum of 8-10 weeks, some dermatologists will recommend up to 12 weeks.

To avoid the risk of your cat eating food from elsewhere such as the neighbour’s house, you will need to confine them indoors for the duration of the trial. If you see a partial response in the first 6-8 weeks then it’s justified to continue the trial for longer. It is very important  that during the food trial you ONLY feed your cat the suggested food. That means they receive no treats, no table scraps and no flavoured worming or flea treatments. If you have a multi-cat household, it is probably easiest to temporarily put all cats on the same diet.

If your cat goes off their food, please call us as soon as possible.

Novel single protein and single carbohydrate diet (Home cooked)

Before selecting a novel protein to use for your cat’s elimination diet, it is important to take time to sit down and create a comprehensive list of all the different foods that they have ever eaten including any treats, table scraps and flavoured medications. This can be difficult if your cat was fed commercial food as this may have contained a variety of protein sources. If finding a novel protein source proves difficult, select one that you know your cat hasn’t eaten the past two to three months. This isn’t always easy.

Natural Balance Delicate Care is a nutritionally balanced commercial dry cat food that has been specifically formulated to help manage skin and stomach problems in cats. It is made exclusively using kangaroo and duck protein, and locally grown sorghum. This diet is suitable for cats that have not been fed duck or kangaroo regularly in the period prior to commencing the elimination diet trial. If your cat also prefers to eat wet food or fresh meat, Delicate Care can be supplemented with cooked meat using a single novel protein such as kangaroo. It is important that before feeding fresh meat to your cat, you firstly discuss with your vet which type of meat they recommend is suitable for your cat’s diet trial. Ensure to only feed meat for human consumption that does not contain any sulphur based preservatives as fatal thiamine deficiencies can occur. 

It is vital that you ensure that your cat only eats the prescribed food that your vet has recommended for the full duration of the trial. This includes all treats and flavoured tablets. Offer your cat only water to drink.

Commercial hydrolysed protein diets

In addition to the novel protein Delicate Care food, there are two additional commercially available veterinary prescription diets that have been designed specifically to be fed as an elimination diet; Royal Canin Hypoallergenic and Hills Z/D. Most cats with food allergies will respond extremely well to these diets however there is a small percentage (approx. 5%) of cats with food allergies that will still react to these diets.

Hydrolysed diets are created based on the knowledge that the vast majority of food allergies are caused by proteins within molecular weight range of 10-70 kDa. Any protein molecules above or below this size will be too large or too small to trigger immune recognition and thus an allergic response. The hydrolysed diets utilise this by breaking down the proteins into very small fragments (below 10 kDa but ideally below 5 kDa).

Interpreting the results of your cat’s food trial

If your cat’s symptoms resolve or dramatically improve while on the diet then this is highly suggestive that they have a food intolerance however it doesn’t make a definitive diagnosis. There is the possibility, albeit unlikely, that their symptoms may have spontaneously resolved with a change in diet.

To confirm the diagnosis, there needs to be evidence that the symptoms recur when elements of original diet are reintroduced. Re-introduce each item one at a time, ideally at two week intervals. A proportion of cats will develop recurrence of signs due to the original diet and this confirms a diagnosis of food hypersensitivity. 30-40% of cases may remain in remission despite reintroduction of the original food and the cause of this unclear.

Disclaimer: Please note that the information provided on this page does not replace the advice of your veterinarian. If you are concerned about your cat’s health in any way, we strongly recommend you seek veterinary advice.