Original article Influence of food processing on the allergenicity of celery: DBPCFC with celery spice and cooked celery in patients with celery allergy Background: Celery root is often consumed in a processed form as a cooked vegetable or as a spice. So far, however, there has been no information about the allergenicity of processed celery in celery-allergic patients. Methods: In 12 patients with a history of allergic reactions to raw or raw and cooked celery, double-blind placebo-controlled food challenges (DBPCFCs) with raw celery (n=10), cooked celery (110uC/15 min; n=11), and celery spice (n=5) were performed. Nine patients underwent an open mucosal challenge with four samples of canned celery retorted at Co-values (cooking effect) of 7.45–76.07 (corresponding to the time periods in minutes at a thermal influence of 100uC). IgE immunoblot analysis of celery extract was performed with sera of all challenged patients. The thermal stability of celery allergen was investigated by enzyme allergosorbent test (EAST) inhibition. Furthermore, intraperitoneal immunization of mice followed by a rat basophil leukemia (RBL) cell mediator release assay was used as a biological in vitro model to assess the allergenicity of processed celery. Results: Six out of 11 patients showed a positive DBPCFC to cooked celery and five out of five patients to celery spice. Allergenicity of celery was preserved in four patients with a positive DBPCFC to cooked celery even if celery was treated at a Co-value of 76.07. Patients with positive DBPCFC to cooked celery reacted to known celery allergens (Api g 1, Api g 4, cross-reactive carbohydrate determinants CCD). EAST inhibition showed that heat resistance of celery allergens decreases in the following order: CCD>Api g 4>Api g 1. Accordingly, five of six patients with a positive DBPCFC to cooked celery were sensitized to profilin and/or CCD. The murine model reflected the reactivity of patients sensitized to the major allergen Api g 1. Conclusions: 1) In a subset of patients with a positive DBPCFC to cooked celery, celery remains allergenic even after extended thermal treatment (76.07 min/ 100uC). 2) Celery spice is allergenic for patients with an allergy to raw celery. 3) RBL cells sensitized with mouse IgE to raw celery may serve as a useful tool for screening the potential allergenicity of heat-processed products containing celery. B. K. Ballmer-Weber 1 . , A. Hoffmann 2 . , B. Wu ¨ thrich 1 . , D. Lu ¨ ttkopf 2 . , C. Pompei 3 . , A. Wangorsch 2 . , M. Ka ¨ stner 2 . , S. Vieths 2 . 1 Allergy Unit, Department of Dermatology, University Hospital, Zu ¨rich, Switzerland; 2 Department of Allergology, Paul-Ehrlich-Institut, Langen, Germany; 3 Dipartimento di Scienza e Technologia Alimentari e Microbiologiche, Milano, Italy Key words: celery allergy; DBPCFC; double-blind placebo-controlled food challenge; food allergy; immunoblotting; processed celery; spice; thermal treatment. Barbara K. Ballmer-Weber, MD Allergy Unit Department of Dermatology University Hospital Zu ¨rich Gloriastr. 31 CH-8091 Zu ¨rich Switzerland Accepted for publication 31 August 2001 Celery (Apium graveolens) which belongs to the Apiac- eae family is a frequent cause of pollen-related food allergy, particularly in European countries (1–6. ). Celery allergy is highly associated with birch pollen and mug- wort pollen sensitization referred to as birch–mugwort– celery syndrome (6, 7. ). Recently allergy to raw celery root was, for the first time, confirmed (8. ) by double- blind placebo-controlled food challenge (DBPCFC). Sera of DBPCFC-positive patients recognized known cross-reactive allergenic structures: The Bet v 1-related major celery allergen, Api g 1, was detected by IgE from 59% of patients, 55% were sensitized to cross-reactive carbohydrate determinants (CCD) and 23% to the celery profilin, Api g 4 (9. ). Celery root is not only consumed raw as fresh salad but also as a cooked vegetable and as a constituent of sauces and soups. Furthermore, dried and powdered celery root is widely used as an ingredient of spice mixtures. Jankiewicz and coworkers have recently investigated in vitro the immunochemical stability of the three known allergenic structures of celery when processed by microwaving, drying, c-irradiation, ultra Abbreviations: CCD: cross-reactive carbohydrate determinants; DBPC- FC: double-blind placebo-controlled food challenge; OAS: oral allergy syndrome; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SPT: skin prick test. Allergy 2002: 57: 228–235 Printed in UK. All rights reserved Copyright # Blackwell Munksgaard 2002 ALLERGY ISSN 0105-4538 228