BACKGROUND Serratial peptidase and lysozyme are often used as anti-inflammatory agents. There have been very few documented cases of occupational allergy caused by these substances. We report a case of a pharmaceutical industry worker who developed occupational asthma and rhinitis caused by both serratial peptidase and lysozyme chloride. OBJECTIVE It is important to alert physicians to the possibility of occupational asthma when dealing with workers in the pharmaceutical industry. RESULTS The patient had strong positive responses to peptidase and lysozyme extracts on skin-prick tests. Bronchoprovocation tests showed a dual asthmatic response to peptidase and an early asthmatic response to lysozyme. Serum specific IgE antibodies to peptidase and lysozyme were detected by enzyme-linked immunosorbent assay (ELISA). In order to further characterize the allergenic component of these extracts, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotting studies were also performed. More than ten components ranging form 7.3 to 83.1 kD were found in peptidase extracts, and two IgE binding components (67, 10.9 kD) were detected within the lysozyme extracts. CONCLUSIONS These findings suggest that inhalation of peptidase and lysozyme can induce IgE-mediated bronchoconstrictions in an exposed worker.