PICKLED ONION-INDUCED ASTHMA - A MODEL OF SULFITE-SENSITIVE ASTHMA

Background Asthma elicited by sulfite ingestion has been mainly descri bed in steroid-dependent and in non-atopic asthmatics. We have studied a group of 18 young extrinsic asthmatics who presented with asthma at tacks immediately after eating pickled onions. Objective The aim of th is study is to ascertain if these asthma attacks are elicited by sulfi tes contained in pickled onions and the influence of the dose and pH o f onions. Methods The bronchial hyperreactivity of the patients was as sessed by a methacholine challenge test. Oral challenge tests were per formed with sodium metabisulfite (MBS) diluted in lemon juice at pH 4. 2 and at pH 3.3 (only in patients who did not react with pH 4.2). Two types of pickled onion, Spanish and Dutch pickled onions, were used fo r oral challenge in seven of the patients. The Monier-Williams method was used to measure the SO2 concentration in pickled onions. Results T he oral provocation test with MBS, pH 4.2, elicited a positive respons e in six patients (33.3%) and the test at pH 3.3 was positive in three out of 12. No significant difference in PD20 values was found between these groups. Three of the seven patients challenged with Spanish pic kled onions had a positive reaction but had no reaction with Dutch pic kled onions. The SO2 concentration in Spanish pickled onions varied be tween 765 and 1182 ppm while in Dutch pickled onions were 200 ppm; thi s exceeded the permitted level (100 ppm). SO2 release in Spanish pickl ed onion samples was nearly 2.5 times higher when the pH of the sample decreased from 4.2 to 3.3. Conclusion High levels of SO2 in Spanish p ickled onions, and their low pH (3.3) would be the responsible factors of the asthmatic outbreaks after ingestion of Spanish pickled onions by these patients.