Seven out of eleven workers occupationally exposed to airborne papain developed immediate hypersensitive reactions, predominantly asthma and rhinitis. Skin tests and RAST with papain were positive in all symptomatic workers, but not in the four asymptomatic workers. Furthermore, out of forty non-exposed asthmatics, thirty-eight had negative RAST results and all had negative skin test results. Bronchial provocation tests with 0.15–0.5 mg papain performed in five patients with a positive case history showed in each case an immediate asthmatic reaction; in addition to that, one patient developed signs of a dual asthmatic reaction.
Our results suggest that airborne papain is a highly immunogenic agent in humans, which induces type I allergic reactions in a large percentage of the exposed subjects.