PETE WEDDERBURN Animal Doctor
for food allergy may be available, the results are inconsistent. In theory, an allergic dog ought to have high levels of food-specific antibodies, but in practice, these have only been identified in research dogs used for allergy studies. Some of these dogs had been bred specially to produce higher than normal levels of antibodies to everything they encounter, so the laboratory results don’t easily translate into real life situations for pets. Scientists are still working on better ways to diagnose food allergy.
Itchy skin due to food allergy can develop at any age, from puppyhood through to old age. The contrasts with allergy to pollens and dusts in the environment (another common cause of itchiness in dogs) which tends to start when a dog is aged between 6 months and three years of age. Another difference between the conditions is that food allergy tends to happen all year round, while environmental allergies tend to be worse when there are more pollens in the air, in the spring and summer. Otherwise, there are many similarities between the conditions: they both cause itchiness and red skin around the face, ears, underside armpits, groin and feet.
A food trial is the only way to diagnose food allergies. A diet containing “novel ingredients” should be used: this means ingredients that the animal has never encountered before, so they cannot be allergic to them. Examples include venison or rabbit meat, with exotic carbohydrate sources such as tapioca. Most people prefer to use a commercially produced diet, obtained via a vet, designed to include only very rare and specific ingredients. Alternatively, a diet containing hydrolysed proteins can be used for the food trial: the ingredients have been “pre-digested” so that their structure is too small to trigger an immune reaction.
The food trial diet must be fed exclusively for 6-8 weeks with no other foods or drinks: just the special food and water. The diagnosis is confirmed if the itchy skin gets better while on the food trial, then recurs when the food item is re-introduced (a so-called “food challenge”). If the itchy skin doesn’t get better on the special diet, food allergy has been ruled out.
If a food allergy is confirmed by a food trial, the cure is simple: the pet must never, ever eat that ingredient again. If he went to restaurants, he’d have to start reading the small print on those menus!