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Food hypersensitivities are common in cats and can present as skin reactions and/or gastrointestinal changes (inflammatory bowel disease (IBD) which was discussed in last month’s blog “Chronic intestinal diseases”). Your vet might recommend putting your cat on an “elimination diet” or a “diet trial” and this can sound quite daunting. 

Elimination diets can be quite arduous due to the length and stringency of the entire process. However, though it may be tricky to manage especially in households with more than one cat, the results can be very rewarding. 

The goal of this particular diet is to identify the specific protein(s) the body reacts to. When a cat is suspected to have a food hypersensitivity, it is commonly due to specific dietary proteins in their food such as chicken, beef and fish. Some less common proteins that result in reactions include pork, rabbit, horse, wheat, corn and eggs. Because reactions to food can present as skin issues and tummy troubles, it is important that a thorough assessment is performed for the presenting problem. For instance, if your cat has gastrointestinal symptoms, this may mean blood tests, faecal tests and abdominal imaging. If your cat has skin issues, this will require a full dermatological work up and a regimented parasite control program. 

Some symptoms of food hypersensitivities in cats include: 

• Excessive scratching, itching and self-induced skin trauma (typically around the head, face, ears, neck and feet). 
• Overgrooming and hair loss (typically over the flanks and the belly, but can be anywhere). 
• Little sores that can be focal or spread across the body (“miliary dermatitis”). 
• Eosinophilic granuloma complex (indolent ulcers, eosinophilic plaques, eosinophilic granulomas). 
• Secondary bacterial and yeast infections commonly
• Vomiting (often hairballs)
• Diarrhoea or bloody stools

Before an elimination diet is started, we must first rule out any other potential causes of the presenting symptoms. This will involve a thorough physical examination and will likely include some follow up laboratory testing such as skin scrapings, cytology, fungal cultures, blood tests, faecal tests and urine tests. Depending on these results, a food elimination diet may be recommended if we are suspicious of a food hypersensitivity. 

Elimination diets are diets that DO NOT elicit an allergic response. There are two ways we achieve this: 

1. Novel (new) single protein source and single carbohydrate source that your cat has never eaten before, not even once. 
2. Commercial hydrolysed veterinary prescription diets- the proteins in these diets are “hydrolysed” (broken down) into such small particles that the body cannot recognise and therefore react to them. 

When introducing your chosen diet to your cat, it is important that we transition their diet gradually over 1-2 weeks as some cats will develop tummy troubles and sometimes food aversions if their food is changed too quickly. This means that your elimination diet does not technically start until your cat is eating 100% of this new diet. Once your cat is eating only the new food, the diet trial continues for a minimum of 8 to 10 weeks. Some dermatologists will recommend up to 12 weeks or longer. 

We expect 50% of cats with food hypersensitivities to respond to this new diet in 4 weeks, 80% to respond in 6 weeks and 90% after 8 weeks. Some cats (about 10%) may take up to 12 to 16 weeks to respond to their new diet. 

During this time, you must be very strict and ensure your cat is not getting any other food (no treats, table scraps, flavoured worming or flea treatments, etc.) that could potentially “contaminate” your elimination diet. Offer you cat only water to drink. Broths or soups may contaminate the diet. In households with more than one cat, it is sometimes easiest to put all cats on the same diet temporarily. If your cat accidentally eats something it shouldn’t, the entire elimination diet should be restarted. 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 to 8 weeks, then it is justified to continue the trial for longer. 

Before you get started though, take the time to compile a comprehensive list of all the different foods (and flavours) your cat has ever eaten. This includes any treats, table scraps and flavoured medications. Sometimes, this can be difficult to determine if they were fed a commercial diet as these often contain a variety of protein sources. If finding a novel protein source is too difficult, select one that you KNOW your cat has not eaten in the past 2 to 3 months. 

Some examples of novel protein sources: 

• Kangaroo 
• Crocodile 
• Rabbit 
• Horse 
• Venison 

NOTE: it is ok to feed just the above meets as sole food for 8 weeks, however in the long term, this will require careful balancing with a veterinary nutritionist. 

Only feed meat that does NOT contain any sulphur-based preservatives as fatal thiamine deficiencies can occur. Meat for human consumption is preferred as it undergoes much more rigorous testing and controls. 

Commercial hydrolysed protein: 

These diets are specifically designed to be fed as an elimination diet. 

• Royal Canin Anallergenic (biscuits) 
• Royal Canin Hypoallergenic (biscuits) 
• Hills z/d (biscuits) 

Most cats with food hypersensitivities will respond well to these diets, however there is a small percentage (about 1-5%) of cats that will still react. Out of the three diets listed above, Royal Canin Anallergenic is thought to be the most superior of the diets, with the hydrolysed protein being the smallest of all the diets, in addition to being made with feather protein as an alternate protein source. 

Monitor your cat closely for improvement or resolution of their symptoms. If they resolve or improve significantly while they are on the diet, this is highly suggestive of a food hypersensitivity, however it does not make this a definitive diagnosis. It is possible, albeit unlikely, that their symptoms may have spontaneously resolved with a change in diet. In order to  confirm that a food hypersensitivity was the cause of the previous symptoms, a “re-challenge” must be done. There must be evidence that their symptoms recur when elements of the original diet are re-introduced. Each item must be re-introduced one at a time and ideally at 2 week intervals. For example, if they were previously on a diet containing chicken, re-introduce chicken and monitor them for any recurring symptoms. If you notice these changes, you can confirm that they are allergic to that protein. 30% to 40% of cases may remain in remission despite re-introduction of the original food and the cause of this is unclear. 

Some cats have multiple allergies or multiple causes of their skin or gastrointestinal symptoms that an elimination diet alone does not resolve. In some of these cases, a specialist dermatologist consult may be recommended. 

If you are struggling with your cat’s elimination diet, feel free to give us a call. Our friendly staff are happy to book you a consult, or give you some helpful tips!

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