Introduction – Unexplained collective syndromes (UCS) are characterized by the simultaneous onset of similar, generally mild symptoms among a group of people sharing a common environment, without any clearly identifiable cause. In January 2022, a residential care facility for adults with autism spectrum disorder (ASD) in Normandy experienced three successive episodes of ocular and skin symptoms affecting residents and staff, leading to several emergency interventions and the partial evacuation of the building.Method – A multidisciplinary investigation (epidemiological, clinical, environmental) was conducted, combining epidemiological, clinical, and environmental assessments. Twenty-seven individuals were involved (13 residents, 14 staff members).Results – Residents presented with observable ocular manifestations, while staff described functional symptoms, such as eye stinging and headaches. The environmental analysis revealed no abnormalities: air and water quality met standards, and there were no technical malfunctions or detectable pollutants. Clinical data suggest a probable infectious origin for the residents’ symptoms, while the staff members’ symptoms are consistent with a psychosomatic illness induced by collective anxiety. Conclusion – This event highlights the influence of psychosomatic phenomena that can manifest in anyone in a context of acute anxiety in the face of an unidentified health threat. It illustrates the complexity of mass psychogenic illness (MPI), combining an initial trigger with psychosomatic reactions among bystanders or individuals exposed to the prevailing anxiety. The study underscores the importance of a multidisciplinary approach to identify, explain, and manage such episodes, as well as the need for clear communication with residents, staff, and affected families to limit the extent and duration of the manifestations.