In Part 1 of this article concentrated on making the diagnosis of possible food allergy. Having done so, the physician may then decide that some form of restrictive diet is appropriate. This article offers some pointers as to how to do this properly. (Note: the term `food allergy' is used below in its widest meaning, to include the more common food sensitivity as well as true allergic reactions).

Whatever the rationale for putting your patient on some form of elimination diet, it is essential that the process be done correctly. Otherwise there is a distinct possibility that you will end up making the patient's situation worse. So the first step in this treatment is to understand the potential pit-falls:

1. Treatment worse than the disease: Compliance with any significant lifestyle change is not easy, particularly if the suspect food is an important part of the person's existing diet, for example wheat or dairy foods. So always bear in mind the impact of treatment on your patient's lifestyle and that of their family.

2. Somatisation: The very act of imposing such an obtrusive treatment produces a real risk that any tendency your patient may have to somatasisation or general hypochondria will be significantly reinforced. This could have particularly serious consequences, for example, in a young woman already inclined towards an eating disorder.

3. Nutritional deficiency: By reducing the number of food choices, you can tip someone with borderline nutritional status into outright deficiency. Iron, calcium or zinc are commonly at risk.

4. Confusion: If the restrictive diet is not implemented properly, you could end up just as confused and uncertain as you were at the beginning of the process, and may even have caused a patient's unfounded prejudices against certain foods to be reinforced rather than educated.

To avoid this pitfalls, here are some practical tips.

Chose your patient wisely . A sensible, motivated and well informed patient who does not have too much emotion invested in their eating patterns is likely to do much better than a marginally malnourished teenage vegetarian with poor body-image for example. Make sure the patient is not looking for an instant cure and understands that the process may take quite some time and patience.

Enlist the cooperation of the family if you possibly can. If the spouse is the one preparing the meals, not seeing them in person is tantamount to therapeutic suicide.

Focus on the positive: Do not concentrate exclusively on what cannot be eaten - encourage the patient to diversify their food choices to compensate for the restrictions you are imposing. This is psychologically wise, as well as a good way also increase consumption of alternative sources of any nutrients at risk. For instance, if dairy foods are to be cut out, suggest the patient explores ways of eating more food sources of calcium and riboflavin like fish, grains and green leafy vegetables.

Define and limit any changes you prescribe are as precisely as possible. If your initial history has led you to suspect a particular food or foods, begin there. This could turn out to be quite simple - the patient appears to react to crustaceous seafood, so you just eliminate this and everyone lives happily ever after. Alas life is not usually so simple! Many foods are present in a wide range of dietary sources, and your prescription needs to be specific and comprehensive. It is not use telling someone to "cut out all acidic fruits" for example -you have to give them an exact list of what can and cannot be eaten.

Wheat, dairy food, soya and certain additives are notorious for turning up in a wide range of food products in forms that are not always obvious to the naked eye. There is also the potential for some cross-over allergy between foods from a common botanical grouping (some grains, solanine-containing vegetables etc.), although this is not usually as important as the mythology might have us believe.

All in all, if you do not have this kind of detailed food knowledge yourself (and few of us do), you may well need to refer the patient for an initial consultation to a dietitian who does, or at least make sure you have some accurate patient handouts.

Resist the temptation expand by tossing in another half dozen foods at the same time, on the grounds that it might increase your chances of getting a good response. This is not usually how it turns out. Compliance with such a complicated regimen is almost guaranteed to be poor, and then when the patient fails to respond to treatment, you will never know if it was because the diagnosis and thus the dietary prescription was wrong, or rather because the treatment was not followed.

On then other hand, if they do respond favourably (and the placebo effect of such drastic lifestyle changes is bound to be strong), you are in for a long and complicated process of tying the improvement down to its source. It is much better to eliminate one food, and therefore one possibility, at a time, even if this means the process drags out over many months.

Three to four weeks is considered the minimum time required for a food restriction to have a positive effect. (There is one exception to this rule of minimum specific change, and this is the total food elimination diet. This is something which requires a good deal of knowledge not to mention some bravery on behalf of GP and patient alike. We may return to it in a future article!)

Monitor and challenge benefits: Once you have the prescription sorted out, make sure you monitor the effects carefully and objectively. This usually means at least a symptom diary, and if in doubt about compliance a further period of keeping a food diary may also be necessary. If the food restriction does reduce the symptoms, the diagnosis is not really complete until a rechallenge with the offending food causes a relapse, and this is cured by food withdrawal for a second time. You may find that the patient resists this deliberate aggravation of their symptoms, but if they are to be stuck with a restrictive caveat on their eating pleasure for a long time to come, it is worth the extra effort at the outset to be sure of the diagnosis.

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Further Resources

1. A good dietitian experienced in food allergy management is every physician's number one resource
2. There is a helpful manual available to assist physicians in implementing food allergy diets. Managing Food Allergy and Intolerance (Janice Joneja et.al) is currently directly from the publishers in Canada: McQaid Consulting fax: 1-604-922 6075; email: <mcg@pro.net>

   Note: The author does not warrant the accuracy or suitablility for any medical, therapeutic or diagnostic purpose of any resource listed.

Return to part 1 of this food allergy article

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