When proteolytic enzymes were first introduced to common laundry detergents in the 1960s, their ability to cause hypersensitivity due to exposure by inhalation was soon recognized as a problem, especially for production workers. Subsequently, formulations and manufacturing methods were developed to minimize exposure to enzymes via inhaled dust particles. Although detergents containing proteases are now considered safe for consumers, the experience with laundry pre-spotter products is not as extensive. Two studies were undertaken to examine the risk of sensitization to protease (i.e. Savinase(®)) used in a trigger-spray laundry pre-spotter product. The first was a laboratory study simulating a very heavy-use scenario in a controlled environment cubical chamber (14.5 m(3)). The product was applied to a series of fabric targets held vertically over a standard washing machine. Eight replicates of the experiment were done, using 30 sprays for each replicate. Airborne particle distributions in the breathing zone were characterized using a TSI particle analyzer. Enzyme concentrations in air were measured using PTFE membrane filters that were frozen until analyzed by an enzyme linked immunosorbent assay (ELISA). Results indicated that aerosol concentrations returned to baseline within 10 min, during which the average enzyme concentration in air was 17 ± 1.6 and 12 ± 0.92 ng/m(3) using low- and high-volume samplers, respectively. The corresponding amount of enzyme that could be inhaled was significantly less than allowed in occupational situations. The second study was a 6-month, controlled-use study involving approximately 100 subjects with confirmed atopic status by skin prick testing with common aeroallergens. The study involved daily exaggerated use of the pre-spotter product for 6 months, with prick testing for the protease carried out at baseline, 3 and 6 months. Results from the clinical study indicated that none of the subjects exhibited reactions that would indicate sensitization to the protease by inhalation. The principal limitations of the study were the relatively small number of subjects and the limited duration (96 completed the entire 6-month exposure program).