An epidemiologic investigation was conducted to ascertain the prevalence of allergic events associated with psyllium in a population of health care workers in long-term care facilities, and to determine if a specific brand of psyllium laxative was associated with the events. Of 743 surveyed health care workers who prepared psyllium laxatives for patients, 136 (18%) reported allergic events. Thirty-four of these employees (5%) reported shortness of breath, wheezing, or hives within 30 minutes after preparing psyllium laxatives. Four hundred thirty-six workers who were exposed to the suspect psyllium laxative were compared with 314 workers exposed to other psyllium laxatives for the occurrence of an adverse event: There was no statistically significant association between exposure to the suspect product and the occurrence of an adverse event. These findings suggest that psyllium laxatives are associated with a spectrum of allergic events ranging from mild to disabling.