True cases of food allergy are unusual and involve a reaction to often only tiny amounts of an ingredient in a particular food, which triggers an allergic inflammatory response. This is not to be confused with more common ‘food intolerance’ which is less severe and involves a different physiological process. True food allergies can occur at any age but are usually diagnosed in young cats. Diagnosis is very difficult, involves diet trials (see below) and there is no specific test available. Studies have shown the offending proteins often include beef, dairy products and fish. The signs of an allergy are not specific and may indicate another problem. Always consult your vet without delay if you observe these signs.
Signs of an allergy
Typical symptoms of food allergies include;
- Skin problems - itching and redness, bald areas or actual abrasions of the skin, usually caused by the cat overgrooming.
- Recurrent ear infections.
- Fur ball problems due to swallowing overgroomed fur.
- Gastrointestinal problems including vomiting and diarrhoea.
- Rarely, respiratory problems.
If you suspect your cat may have a food allergy, consult your vet. Never try to treat such a problem yourself; diet trials must be closely supervised by your vet, otherwise nutritional problems or deficiencies may result, or your cat may have another problem requiring different treatment.
Testing for allergies
The most effective method of testing for an allergy is called an exclusion diet trial, where a cat is put onto a bland diet, often a hypoallergenic diet where the proteins in the diet are so small they cannot (or very rarely) cause an allergic reaction. Alternatively a diet containing proteins and carbohydrates your cat has not eaten before, such as venison and rice, is recommended. Commercial diets are available, and some vets will advise a diet cooked at home. The duration of the exclusion diet depends on the type of problem: in cases of skin problems, for example, the diet generally needs to be maintained for from 4 to 12 weeks, sometimes longer; with gastrointestinal problems an improvement in signs is usually seen more rapidly. This diet must be the only thing the cat eats for the duration of the trial, so no treats or titbits are allowed. It can be very difficult to stick to such a diet, especially if you have more than one cat, so be honest if you do slip up, and consult your vet if your cat won’t eat the new diet. Some hunting cats will need to be kept indoors to ensure the occasional mouse doesn’t form part of the diet!
After the trial period
Once your cat has finished the trial period, your cat should be re-assessed by your veterinary surgeon. If no improvement has been noted, investigations into other diseases should be undertaken. If there has been an improvement then your vet will advise you on the next step. This will depend on your cat’s specific problems and may involve reintroducing proteins to the diet and monitoring for a reaction (provocation). If the symptoms return when a food is reintroduced, you may have your culprit. There may be more than one food type responsible. This process is difficult and must be closely monitored. In some cases if the cat’s clinical signs have been severe, and the diet that has resulted in an improvement is complete and nutritionally balanced, owners and vets may decide to continue feeding that diet in the longer term.
The process requires time and patience and your cat may need to be referred to a veterinary specialist to oversee the diet trial. Contact your vet if you suspect your cat may have an allergy.