Épidémiologie de l’allergie alimentaire

The epidemiology of food allergy normally relies on surveys using questionnaire in general populations and studies on cohorts and through professionals in allergy clinics, sometimes completed by prick-tests, specific IgE assays and/or oral challenges. Complementary data are supplied by specialized medical networks. In European countries, the prevalence of food allergy in the pediatric population is about 4.7%, and in adults it is about 3.2%. Striking disparities characterize the response to questionnaires in EU countries. Life-threatening anaphylaxis occurs in 1/10,000 inhabitants, fatal anaphylaxis in 1/1 million inhabitants. A drastic increase of life-threatening and lethal anaphylaxis has been noted in the UK and Australia over the past ten years. In France, there has been an increase of 28% between 2001 and 2006. The Allergy Vigilance Network, which includes 400 allergists, reports that this increase has occurred in the pediatric population. The prevalence of food allergies depends on age and consuming habits. Milk, egg, peanut and tree-nuts are at the top of the list in children. Prunoïdeae, latex-group fruits, Apiaceae, wheat and tree-nuts are the most important food allergens in adults. Peanut and tree nuts are the main offending allergens in severe anaphylactic cases. Since 2002 the Allergy Vigilance Network in France and Belgium has been identifying newly-appearing dangerous allergens. Molluscs, lupine flour and cashew nuts are the most common on this list and labelling these foods is now compulsory. Goat and sheep milk proteins (14 cases), buckwheat (25 cases) and wheat isolates are not yet required to be labelled. The danger of anaphylaxis to goat and sheep proteins (two deaths out of 14 cases) is due to the likelihood of their being masked allergens, for which reason the EU Scientific Agency should be made aware of the necessity of required labelling of foods containing these substances.     

Optimal management of atopic dermatitis in infancy

The necessity to optimise the management of atopic dermatitis of infants needs knowledge of three components: increase of prevalence, extreme frequency of food allergy and increase in the frequency of the syndrome of multiple allergies, that frequently develops into asthmatic disease. Management of DA in infancy (first year of life) is based on the global strategy of understanding the physiological Th2 polarisation at birth, that does not allow a re-equilibration of the Th1-Th2 balance that progresses in the first six months of life (in normal infants) making in this period a window of opportunity for sensitizations. Prevention in high-risk children (familial history of atopy) covers the non-exposure to in door pollutants (tobacco and volatile organic compounds), breast-feeding or a hypoallergenic formula for a hydrolysate of pork and soya proteins or better an extensive hydrolysate of casein. Four situations require moving to an amino acid substitute: failure to thrive, severe atopic dermatitis, a syndrome of multiple food allergies, allergy to hydrolysates. Reintroduction of foods should be considered with the least delay so as to induce digestive tolerance. It should take into account the clinical development, the intensity of the sensitisation and eventually depend on a realistic test of introduction. Management of DA searches for recovery of generalized eczema, failure to immediate improvement of quality of life prevention of immediate complications (local sepsis) acceleration of return to food tolerance. Prevention of ulterior development of asthma by immediately introducing measures to diminish respiratory exposure to allergens and tobacco is hoped for.     

Comparative evaluation of RAST and FAST for 11 allergens in 288 patients

The specific IgE levels for 11 allergens were compared in 288 patients by means of the Phadebas RAST and the IgE-FAST. Agreement (less than 1 class difference) was observed in 78.7% of the cases. The best agreement was observed with Phleum pratense, egg white, corn, Betula verrucosa and cat epithelium. In 91 cases the results were retrospectively compared with clinical data and skin tests. When RAST and FAST differed (n = 31) 93.5% and 51.6% of the respective results were in agreement with the skin test. When RAST and FAST were similar (n = 60) 81.7% and 80.0% of the respective results were in agreement with the skin test. It was concluded that the RAST and the FAST gave similar results in most cases but that the RAST was more sensitive than the FAST, especially when the results obtained with both methods differed.     

Clinical evaluation of in vitro leukocyte histamine release in allergy to muscle relaxant drugs

We have evaluated the in vitro leukocyte histamine release tests for the diagnosis of allergy to muscle relaxant drugs in 40 patients (Group A) and a control group of 44 subjects with negative leukocyte histamine release (Group B). Non-IgE dependent histamine release, expressed as a percentage of the total blood histamine, was 3.94% +/- 0.49 in Group B. The upper limit of positivity was estimated to be 5% (mean + 2 SD). Leukocyte histamine release tests were positive in 65% of the patients from Group A. The concordance between LHR and QAS-RIA was 64%. The maximal histamine release was observed at dilutions of 10(-2)-10(-4) in 20 of the 26 positive cases. The maximal histamine release was 43.8% +/- 23.3. The spontaneous histamine release was as low as 1.7% +/- 1.1. Cross-reactivity among the 5 different muscle relaxant drugs has been investigated and compared by intradermal testing. The muscle relaxant drugs which gave the lower skin reaction (M2) and the drug responsible for shock (M1) were selected for the study of in vitro leukocyte histamine release. Of 20 M2. All of the 10 cases had negative ID tests with M2. Three of these patients subsequently underwent general anesthesia with the muscle relaxant chosen as harmless (M2) without any clinical reaction.