Background: Since March 2000, a series of infants with serious gastrointestinal and neurological symptoms have been observed in Spain. These symptoms were suspected to be associated with the use of star anise infusion. We performed an epidemiological study to determine the characteristics of these patients and to evaluate the association between the symptoms and anise consumption.
Method: From February to September 2001, a matched case-control study (1:2) was performed among infants aged less than 3 months admitted to the pediatric emergency departments of two hospitals in Madrid. Mantel-Haenszel and conditional logistic regression odds ratios (OR) were calculated to quantify the association and the dose-response relationship. Laboratory analyses of the implicated substances were performed.
Results: Twenty-three cases were studied. The mean age was 29.2 days (SD: 25.5). The symptoms observed were irritability, abnormal movements, vomiting and nystagmus. Eighteen cases and 36 controls were included in the case-control study. Nine controls (25 %) consumed anis infusion (consumption was high in five and low in four). The Mantel-Haenszel OR was 18.0 (2.03-631) and the OR for the dose-response relationship was 11.7 (95 % CI: 1.3-188.5) for low levels of consumption and 18.2 (95 % CI: 1.8-183.5) for high levels. Laboratory analyses revealed contamination of Illicium verum by Illicium anisatum.
Conclusions: This study confirms the association between the symptoms described and the use of anise infusion. The dose response analyses provide further evidence for the association. Cross-contamination was found between the product and other anise species. We recommend destruction of the contaminated products, avoidance of anise infusions among infants, and dissemination of the results among pediatricians.