Spa Treatments Face Scrutiny Over Potential Infectious Risks and Lax Oversight
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France’s High Council of Public Health (HCSP) has raised concerns about potential health risks associated with spa treatments, particularly those utilizing natural sludge, due to a lack of standardized monitoring and regulation.
A recent opinion from the HCSP indicates that a significant portion of spa-goers – potentially over 300,000 patients annually – could be exposed to poorly monitored infectious risks. The core of the issue lies with the sludge derived from natural waters, a component of treatment for at least 60% of spa guests, often involving nine to eighteen applications as prescribed by a spa physician. Between three and six million sludge treatments are administered each year.
Concerns Over Sludge Quality and Regulation
Currently, the quality control of this sludge is not standardized or legally mandated. While a “guide to good thermal practices,” developed collaboratively by the industry and the Directorate General of Health (DGS), exists, its application remains voluntary. Similarly, guidelines for hydrothermal treatments proposed by the French Union of Thermal Physicians (SFMTh) are also not compulsory. Critically, France lacks a dedicated system for monitoring potential health threats originating from thermal spas.
Despite a high average compliance rate of 98% in analyses conducted as part of health controls between 2015 and 2017 – with 29 establishments receiving notices and five facing closure – the HCSP emphasizes the lack of systematic analysis. “The sludge is not subject to systematic analysis of its quality,” the report states, highlighting the variability in clay types, preparation methods, application techniques, conservation practices, and disinfection procedures. These factors are “not sufficiently identified, accessible, brought to the attention of the authorities and the public.”
Only 21 establishments participating in the Aquacert certification process, based on best practices, undergo routine microbiological testing for pathogens like Legionella sp., Legionella pneumophila, E. coli, staphylococci, Pseudomonas aeruginosa, and enterococci. While these certified facilities demonstrate strong compliance, the HCSP has observed a decline in the percentage maintaining a 100% compliance rate annually.
Legionnaires’ Disease and Adverse Effects
Public Health France recorded 10 cases of Legionnaires’ disease linked to spa visits in 2025, a figure consistent with the 8-18 cases reported annually since 2021. In response, the HCSP is advocating for the implementation of more stringent standards for quality testing.
Beyond infectious risks, the HCSP also points to limited research on the adverse effects of thermal treatments. A study of 33 randomized trials found that treatments were discontinued in 2.8% of cases for patients with chronic low back pain, with thermal treatment potentially implicated in 2% of those instances. For patients undergoing treatment for knee osteoarthritis, treatment was stopped due to adverse effects in 0.5% of cases, 0.35% of which were attributed to the treatment itself. However, the HCSP notes that these studies reflect a diverse range of treatments, making definitive conclusions difficult. “.
The HCSP stresses the need for a comprehensive, nationwide vigilance system to accurately assess the benefit-risk profile of thermal treatments.
Chemical Risks and Funding Concerns
The HCSP’s review also extended to the products used to purify and disinfect natural mineral waters, identifying potential risks from substances that are carcinogenic, cytotoxic, or genotoxic. While these products are controllable, a formalized protocol for addressing exceedances of safety thresholds is currently lacking.
The 110 thermal establishments operating across 90 resorts in France are reimbursed by Social Security but do not officially qualify as healthcare facilities. Authorization is granted by the Ministry of Health, following advice from the National Academy of Medicine (ANM), for one or more of twelve recognized therapeutic areas.
Adding to the uncertainty, a proposed government measure to reduce reimbursement rates for thermal treatments – potentially saving 200 million euros – was initially considered during debates over the 2026 social security financing bill. While ultimately rejected and absent from the final legislation published on December 30th, the possibility of future dereimbursement remains a concern, potentially achievable through a simple decree.
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