In many journals recently editorial are found about the indicence (frequency) of food allergy and intolerance. (German studies shows 20% of people have allergy or intolerance. CAM, January 2002).

The source of this article is based on a research of Dr. Schäfer published in a book in 1996 titled Food allergies and intolerance's of G. Eisenbrand et al. In this book there is chapter of Dr. T. Schäfer et al. titled Epidemiology of adverse food reactions due to allergy or other forms of hypersensitivity. Why is this news in 2002? Because in Allergy 56 an article appeared from the same author with the same content. Now the article is rediscovered.

A German study has disproved recent claims that food allergy and intolerance is not widespread (see CAM, January). Based on a survey of more than 1500 adults, the researchers say that around 25% of people showed sensitisation in skin prick tests.

Nuts, fruit and milk cause the most reactions and hay fever is a frequent concomitant condition for adults with food allergy, report scientists from Technical University and Ludwig-Maximilians University, both in Munich, and the Institute of
Epidemiology in Neurenberg.

The investigators interviewed participants to obtain detailed information on food allergy/intolerance and any history of atopic disease. They also did skin prick tests with ten common foods and nine aeroallergens.
The scientists said that food allergy and intolerance was reported by 20.8% of the people in the study, almost identical to the results of a large population-based study in the UK (19.9-20.4%), and higher than the results of a Dutch study. Other studies have revealed results varying between 4.9% and 33%, they say, while in an earlier German population-based study of 910 adults, they themselves found a reported frequency of food intolerance of 18.8%. Similarly, 25 of 1812 adults in a Swedish study gave a history of adverse reactions to food.

The researchers acknowledge that this high level of incidence is in marked contrast to epidemiological studies which have used double-blind, placebo-controlled food challenge to investigate food allergy and intolerance and resulted in the much lower estimates of between 1.4 and 2.4%. But they say that these studies have limitations due to

• the small numbers tested (73 and 93, rather than hundreds)
• the selection process
• the fact that in one study a standard battery of eight allergens were tested, allowing inferences only on these substances
• the type of reactions, which were to some extent only loosely related to FA/FI (headache, and behavioural and joint symptoms).

Overall, 20.8% of the 1537 studied subjects (50.4% female, age median 50 years) reported food allergy or intolerance (women 27.5%, men 14.0%). Nuts, fruits, and milk most frequently led to adverse effects, and the sites of manifestation were oral (42.9%), skin (28.7%), gastrointestinal (13.0%), systemic (3.2%), and multiple (12.2%).

One-quarter of the subjects (25.1%) were sensitised to at least one food allergen in the prick test, with hazelnut (17.8%), celery (14.6%), and peanut (11.1%) accounting for most of the positive reactions.
Food-allergic subjects (positive history and sensitisation to corresponding allergen) suffered significantly more often from urticaria, asthma, atopic eczema, and especially hay fever (73.1%) than controls (3.0%). Furthermore, hay fever was treated significantly more often in subjects who suffered from concomitant food allergy.

The researchers believe that there is a cross-reactivity between pollen and food allergens. Within the group of food allergens tested, they found a strong association of sensitisation to soy and celery or hazelnut, as well as sensitisation to celery or peanut and hazelnut. This clustering indicates cross-reactivity between food and pollen allergens causing food allergy in adults as a sequel to pollen sensitisation. More than 70% of subjects with food allergy, as defined by history of food allergy or intolerance and sensitisation, had a history of doctor-diagnosed hay fever. A strong and clinically relevant association of food and pollen sensitisation is known from several patient-based studies and gave rise to descriptions of clinical entities such as the celery-carrot-mugwort-syndrome.

Food allergy was also found to be significantly associated with other outcomes of atopy in this study. They estimate that 65% of those with food allergy exhibit other clinical manifestations of atopy. Associations of food allergy or sensitisation with asthma and bronchial hyper responsiveness have also been reported.

As long as the results are based on the skin prick test in which the result is only positive when a reaction occurs within 15 minutes, the frequency which is found in this kind of research is still underestimated. Firstly it is proved that the same skin prick test can be positive if another dilution of the same allergen is used. Secondly only a few allergens are investigated in this kind of research. The secondary allergy reaction some times called food intolerance test. This kind of reactions shows a response after 8-12 hours and a secondary response after 2-3 days. In the skin prick test the reaction is often seen after 8 hours or the next day.

Schäfer, T. et al. (2001) Epidemiology of food allergy/food intolerance in adults: associations with other manifestations of atopy. Allergy 56, 1172-1179.

Young, E. et al. (1994) A population study of food intolerance. Lancet 343, 1127-1130.

 Schäfer, T. and J. Ring (1996) Epidemiology of adverse food reactions due to allergy or other forms of hypersensitivity. In.: Food allergies and intolerances (Eisenbrand, G., H. Aulepp en A. Dayan, ed.) DFG Symposium, Weinheim, VCH Verlag, 40-54.