On June 16, 2017, a departmental union chapter reported cases of ENT and skin irritation among physical therapists working at a spa in the Hérault department to various regional administrative authorities, including the Occitanie Regional Health Agency (ARS). This report was handled by the Occupational Health Alert Group (GAST). A three-pronged investigation (epidemiological, technical and toxicological, and regulatory) was conducted. The simultaneous onset of several cases of skin and ENT symptoms over a period of approximately two months suggests the existence of a cluster of cases with a persistent common source of exposure in the workplace. This occupational exposure occurred in a context of poor disinfection practices using the active ingredient PHMB and inadequate ventilation of the premises. The symptoms presented by the physical therapists are consistent with the documented health effects of PHMB. The architectural layout of the massage rooms, the water and ventilation systems, as well as the results of the technical tests and the epidemiological investigation, indicate that all of the rooms are potentially affected by the issue. Several proposals have been made: work to improve airflow in all treatment rooms, replacement of the active ingredient PHMB, and training of staff on chemical risks. Finally, a national report was submitted to the agency responsible for evaluating the active ingredient.