Introduction: On June 12, 2014, suspected cases of swimmer’s dermatitis in a body of water in Puy-de-Dôme were reported to the Auvergne Regional Health Agency (ARS). Since this type of report had rarely been documented in Auvergne, environmental and epidemiological investigations were conducted to confirm the etiology, describe the outbreak, and identify risk factors. Method: A case-control study was conducted by the Auvergne Regional Health Surveillance Unit (Cire) using a sample of individuals who had visited the water body during the weekend of June 7–9, 2014. Environmental investigations (sampling and analysis of bathing water and gastropods) were conducted by the ARS. Results: Thirty questionnaires (21 cases and 9 controls) were completed. All cases had bathed and rapidly developed pruritus after swimming. The maculopapular rash, which began in most cases within 24 hours of swimming, spread over the entire body (62%) and lasted 10 days or longer (60%). Swimming at developed beaches was associated with a higher risk of swimmer’s dermatitis compared to an undeveloped site (p<0.05). Gastropods were identified (family Lymnaeidae, genus Radix) and furcocercariae were observed in the bathing water. Conclusion: The clinical characteristics, as well as the identification of the gastropods (Radix) and furcocercariae, confirmed the diagnosis of swimmer’s dermatitis. Effective management measures were quickly implemented. This study described this first significant episode of swimmer’s dermatitis reported in Auvergne and proposed a protocol for responding to other reports of this type.