Natural Mineral Waters (NMWs) can be used in a thermal spa according to three main methods, in line with the administrative classification of hydrothermal treatments:

• External treatments, where the NMW comes into contact with the patient's skin in various forms and can be inhaled (baths, showers, sprays, mist sprays, or steam, etc.);
• Internal treatments: the NMW comes into contact especially with the oral, vaginal, and rectal mucous membranes;
• Drinking therapy, widely used for metabolic diseases, where the patient ingests quantities of NMW prescribed by spa physicians, both at the thermal spa and possibly at its accommodation.

In response to a request from the General Directorate of Health, the High Council for Public Health (HCSP) has issued recommendations concerning the microbiological quality limits of thermal waters; the physicochemical and microbiological quality requirements for thermal pools; the procedures for managing non-conformities. the rules for the design and installation of thermal pools; the maintenance of thermal water networks; and the monitoring of sludge.

In addition, the HCSP recommends the establishment of a working group to update the ministerial guidelines published in 2005 on water in healthcare facilities and the implementation of a national monitoring system, aiming to:

• improve knowledge of adverse effects related to spa treatments, whether they occur during the treatment or in the month following it;
• identify patient profiles or pathologies that may present an increased risk of adverse effects;
• reliably assess the benefit/risk ratio of spa treatments in their various forms.