Respiratory complaints and high sensitization rate at a rennet-producing plant

Workers in a rennet producing plant reported airway symptoms, mainly rhinitis. Rennet was produced as fluid and powder with proteolytic enzymes as the active component.

Data on airway symptoms and known allergies were collected and skin prick tests (SPTs) with the rennet types produced in the plant and standard allergens were carried out on 35 plant employees. An identical SPT was carried out on 28 controls without known exposure to rennet.

Twenty-one employees (60%) had hay fever-like symptoms, 10 cases mainly at work. Nine had mild to moderate asthma-like symptoms, in six cases related to the work place. Fourteen had a positive SPT to one or more rennets. The sensitization rate was highest among employees with regular contact to rennet powder.

Rennet is a potent allergen. Respiratory symptoms and sensitization can occur in connection with rennet exposure, especially as a powder.