Food intolerance & allergies

If you bring your pet to a veterinary surgery with a complaint of itching or digestive distress, your veterinary surgeon will first rule out more common causes of these signs. The rule-out process might include a physical examination and laboratory tests for flea allergy dermatitis, the most common cause of allergic skin disease of animals, inhalant allergies, seasonal reactions to pollen, mould spores, and dust mites, and food caused digestive intolerance, an acute adverse reaction to food that does not involve the immune system.

If the food allergy remains a suspect, your veterinary surgeon will then help you try to pinpoint what might be causing your pet's problems. Most food-allergic dogs are hypersensitive to only one or two ingredients, with beef and dairy proteins topping the culprit list.

Ingredients that may also cause problems - but not as often - include grains, pork, chicken, eggs, and fish. Allergies to food additives including preservatives may also be a cause but are rare.

Once diagnosed, healing the problem is not so easy, made worse because of a lack of legislation governing pet food labelling, which means pet owners cannot always clearly identify what they are feeding their pets. Pet food manufacturers are currently not obligated to name actual ingredients and some pet food labels use general terms such as 'meat by-products' and 'cereal or animal derivatives'.

Treating an intolerance

A few points as to the possible course of action your veterinary surgeon may suggest:

1. Firstly, just changing from one commercial diet to another is probably not going to solve the problem, as it is difficult to know precisely what is is in a particular food, as labelling regulations are not tight enough.

2. An elimination diet is the only sure way to work out a) whether the problem is food related and b) what's causing the problem. An elimination diet is most often a bland diet of very well cooked rice with a single source of protein - Elimination diets for dogs include lamb, chicken, rabbit, horse meat and fish as sources of protein, with rice or potatoes. Successful elimination diets for cats include lamb, chicken, rabbit or venison, with rice. All other foods, treats, table scraps and tit-bits must be eliminated from the dog or cats diet. Elimination diets fail when the owner or someone else takes pity on their pet and introduces a treat before the end of the trial, the dog or cat managed to scavenge or find food from another source, the dog or cat is actually intolerant to one of the ingredients in the elimination diet or the dog or cat is suffering from factors other than food intolerance.

3. The diagnosis is conclusively proven by reproducing the symptoms by feeding the original diet after the elimination of signs on the new diet. The pet can then be fed on a commercial diet (or home-made food) without the offending allergen(s).

4. Unfortunately this is not a quick process, and the elimination diet should be continued until signs of the problem have gone. This process could take up to 10 weeks, as the study below shows:

5. If there are improvements the owner can then start to reintroduce other food items one at a time in order to determine what the animal is reacting to. Experts recommend that each new food must be introduced two weeks apart as some ingredients may cause a delayed reaction.

6. There is no cure for food allergies. Managing a food allergy means simply avoiding the causative ingredient or ingredients. Medications (such as antihistamines and corticosteroids) that reduce itching caused by other types of allergies don't always work on food-induced itching.