A cross-sectional study of 125 pharmaceutical workers engaged in the manufacture of bulk laxatives based on ispaghula husks (psyllium) and senna pods was conducted. Skin prick tests with extracts of these components revealed that 7.6% were allergic to ispaghula and 15.3% were allergic to senna. Four (3.2%) cases of occupational asthma were identified. The overall prevalence of asthma (6.4%) was less than in a comparable nonexposed Australian population (odds ration, 0.44). Symptoms referrable to the upper airways, eyes, and skin were more prevalent (52.0%) than in the reference population (odds ratio, 1.53). Smokers and nonatopic subjects were more likely to complain of these symptoms if they were sensitized to senna and/or ispaghula than if they were not sensitized (relative risks, 1.9 and 2.6, respectively). Sensitization to ispaghula and/or senna was not a risk factor for asthma. An IgE-mediated allergic mechanism is probably responsible for the allergic symptoms in many of these subjects. Smoking seems to be a cofactor in this process.