Sulphur dioxide sensitivity in South African asthmatic children

Sulphur dioxide (SO2) is a well-known precipitant of asthmatic attacks. Many foodstuffs are preserved with SO2 and other sulphites. In this study 37 asthmatic children attending the Allergy Clinic at the Red Cross Children's Hospital were challenged with SO2 in apple juice in a dose similar to that commonly ingested in soft-drinks containing this preservative. The responses of these children were compared with the responses of 22 asthmatics challenged with apple juice alone. Sixteen out of 37 children (43.2%) challenged with SO2 reacted with a fall in forced expiratory volume in 1 second (FEV1) of more than 10% compared with none of the 22 control asthmatic children challenged with apple juice alone (P = 0.0016). Girls were found to be more sensitive than boys. A 20% or more fall in FEV1 occurred in 8 (21.6%) of the children challenged with SO2 compared with none in the control group (P = 0.039). There was an individual variability in the responses of sensitive individuals to the SO2 challenge. Reactions occurred in spite of maintenance medication and occurred within 5-30 minutes of challenge. Since sulphite sensitivity is common in asthmatic children, ingestion of sulphites should be avoided.