Food allergy - an Increasing challenge for epidemiologists, clinicians and industry

The real challenge for the epidemiologist in food hypersensitivity (FH) is that no reliable and simple method for its diagnosis exists. Questionnaires do not fulfill the requirements of specificity, suggesting data for point prevalence between 0.0.. and < 10.0 %, and the easiest method for epidemiological purposes, screening via specific IgE determinations alone is also generally rejected.

The individual diagnosis of FH (and intolerance) consists of 1) collecting information and 2) the use of decision algorhythms, respecting probabilities.

Information should include all previous anamnestic data: diseases, presumably unrelated symptoms, laboratory results, diets, pharmacotherapies. These data may help in identification of the underlying abnormality of the mucosal/gastrointestinal immune reactivity, and/or the changes (mostly increase) of the intestinal permeability (resulting in increased antigen challenge).

The latest may be the result of chronic medication (e.g. nsaid).The former consists of IBDs, Helicobacter infection, gallstones etc.

Family history (mother and offsprings) helps to identify not only atopy prone families, but common dietetic characteristics as well.

Symptoms, although important for monitoring, often do not offer significant help in differential diagnosis.

Databases, characteristic for each country and region, should contain not only components of foodstuff and presence or absence of additives and hidden food but consumer preferences, industrial technologies as well. The globalization of the food market imperatively demands international databases too. Further databases should contain the continuously growing number of cross-reactivities (mainly among pollens and fruits, vegetables, spices etc.) and the commonly used home (cosmetical), office and workplace chemicals.

Originally, a precise food diary (including symptoms and general medication if applicable) is the greatest help in the identification of individual offending foods. The greatest mistake in the preparation of such diaries is, if the complying patient tries to delete any offending food from her/his diet depriving the investigator of many informations. Diaries should be prepared under unchanged conditions for at least one month.

The philosophy in the diagnostic process in FH is to exclude as many suspicious food components as only possible by means of anamnesis, skin tests, "static" parameters as specific immunoglobulins (i.e. IgE, as no others are really informative in most cases) and some times "dinamic", functional parameters like ECP, histamine, tryptase or leukotrienes – preferably during open food challenges.

Although the double-blind placebo-controlled food challenge (DBPCFC) is the "golden standard" of the diagnosis of FH, it has many drawbacks: it is time consuming (unless the reduction of the number of possible provoking agents is successful in previous steps), the DB character is technically difficult for larger food quantities, which only provoke symptoms in individuals of moderate sensitivity, and patients who are not completely symptom-free are unsuitable for such trials. (Changes in the intensity of symptoms depend on so many factors that cannot be accepted as reliable proofs of established FH). Therefore, the usual exclusion diets cannot be used unless there is good evidence of a single offending, not cross-reactive food allergen (or additive). More effective and faster is the method of introducing a very low allergen diet (VLAD) and using the inclusion type of diets for provocations.

The characteristics of VLAD include the local features of nutritional traditions and avoidance of all major allergens. VLAD, however, may represent an insignificant calory and protein malnutrition for the periode of DBPCFC.

The VLAD is not only the means for making the patient under investigation temporarily but completely symptom free in less than one week's time (valid for approximative 50 % of all investigated patients) but is the only diagnostic possibiliy, if more that one basic food component is included into the list of suspected allergens. If the prerequisite of symptom-symptome-free periods cannot be met, no reliable diagnosis with our present in vivo methods can be done.

Today's therapy is rather conservative (avoidance diets, and if fail, pharmacotherapy). Special formulas, probiotics, functional food and dietary modifications of PUFA-intake are also today's more conservative options. Allergen specific immunisation (SIT) is in its present form usually a failure.

Immediate measurements to avoide food-induced anaphylaxis are epinephrine containing self-injectors and emergency action plans (to be prepared individually and discussed well in advance !).

The future of FH seems more bright: our perspectives for the effective management of food hypersensitivity will improve. On larger scales, the careful planning of GMOs will reduce allergenic potential. The use of gene manipulation techniques improves diagnosis and helps to redirect (instead of eradicate) immune responses: to reestablish oral/mucosal tolerance. At present, monoclonal anti-IgE antibodies, antigen-cytokine fusion proteins, naked plasmid DNA, and immunostimulatory CpG motifs are most investigated.