Many questions arise when a paediatrician prescribes thermal treatment. Answers to these questions have come to light in recent literature. For paediatric indications, thermal treatment is dominated by asthma and its allergic equivalents. In such cases, sodium chloride and bicarbonated spas are used. Such indications are based on the research of the Pasteur Institute for Le Mont-Dore spa and on different modifications of intracelllular enzymes and increase of resistance to hypoxy incited by the La Bourboule spa. The waters in the spas of the Pyrenees contain sulphur, and are mainly used for the treatment of chronic or repeated ENT infections. Fundamental studies in favour of thermal treatment have only aroused indirect views. Following the enquiry made by the French National Health Service on 3,000 patients over a period of 3 years from 1983, it was found that this treatment reduces medical consumption, doctor's visits and hospital care in many cases. However no double-blind research could be performed despite the desire of several spas. These spas improve either the quality of the final product or the strict hygiene level in the thermal installations, and also the sanitary educational measures associated with thermal treatment.