True cases of food allergy in dogs 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 the more common ‘food intolerances’, which are less severe and involve a different physiological process. True food allergies can occur at any age but are usually diagnosed in younger dogs. Diagnosis is very difficult, involves diet trials (see below) and there is no specific test available, with results of tests such as blood tests unreliable. Studies have shown offending proteins often include chicken, eggs, lamb or soy. A specific food allergy has been well documented in Irish Setters: sensitivity to gluten. 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, with bald areas appearing. Feet, face, armpits and groin are often affected.
• Recurrent ear infections.
• Gastrointestinal problems - vomiting and/or diarrhoea.
• Rarely, respiratory problems.

If you suspect your dog 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 or nutritional problems/deficiencies may result, and your dog 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 dog is put onto a bland, often hypoallergenic, diet, where the proteins in the diet are so small they cannot (or very rarely) cause the allergic reaction. Alternatively, a diet containing proteins and carbohydrates your dog 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 general, for skin problems the diet 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 dog 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 dog, so be honest if you do slip up, and if your dog will not eat the new diet consult your vet.

After the trial period

Once your dog has finished the trial period, he or she 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 dog’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 where the dog’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 dog may need to be referred to a veterinary specialist to oversee the diet trial. Contact your vet if you suspect your dog may have an allergy.