BACKGROUND Although there have been a few reports of occupational asthma due to cellulase in several occupational settings, this is the first case of cellulase-induced occupational asthma in an employee working in the textile industry. Its pathogenetic mechanism remains to be further clarified. OBJECTIVE It is important to alert physicians to the possibility of occupational asthma caused by cellulase in workers of the textile industry. RESULTS The patient had atopy and strong positive responses to cellulase extract on skin prick tests. Bronchoprovocation test showed an early asthmatic response to cellulase extract. Serum specific IgE and specific IgG4 antibodies to cellulase were detected by enzyme-linked immunosorbent assay (ELISA). In order to further characterize the allergenic component of the extract, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotting studies were performed. Eight IgE binding components ranging from 6 to 97.5 kD were detected within the cellulase extract. CONCLUSIONS These findings suggest that inhalation of cellulase can induce IgE-mediated bronchoconstrictions in employees working in the textile industry.