Involvement of raw and heated egg yolk in children food allergy to egg
Résumé
Food allergy to egg is commonly diagnosed in childhood with good prognosis. Egg white (EW) is considered as the main culprit but egg yolk (EY) retained less attention and its clinical involvement remains unclear.
Children with food allergy to egg were recruited and undergone skin prick-testing (SPT) with raw and hard-boiled EW and EY fractions, carefully prepared to avoid any cross-contamination. Specific IgE-binding towards EY in sera were determined by ELISA.
Fifty-four children (15 girls; 3.8 ± 1.7 years old) were recruited. They mainly suffered from urticaria with both raw and cooked egg. All children had positive prick-tests to raw EW (mean diameter: 12.6 ± 7.0 mm) and 39 (72%) to raw EY; the mean of positive diameters was 8.8 ± 5.1 mm for EY. After hard-boiling, 36 (67 %) children still had positive SPT to EW and 15 to EY (28 % of the cohort, 38 % of children with positive SPT to raw EY) and means of positive diameters were 10.8 ± 5.6 mm for EW and 4.9 ± 2.1 mm for EY. Among egg yolk fractions, IgE in sera more frequently bound to lipovitellenins/LDL (36%) and livetins (34%) fractions than to lipovitellins/HDL (18%) and phosvitins (5%) fractions.
Beside egg white, children with food allergy to egg appear to be more frequently sensitized to EY and reactive to raw and heated EY than generally assumed. Their IgE-reactivity to EY is mainly directed toward the plasma EY fraction.