It involves conducting a clinical study on a population of healthy volunteers (age between 18 and 30 years) without direct benefit for the subject to explore a transfer of barium in the blood and urine following applications of thermal mud. The main objective is to highlight an increase in serum barium level of at least twice.

The presence of barium in thermal clays was noted by the ARS (french administration) who interviewed the Directorate General of Health (DGS); the latter seized the National Academy of Medicine (June 2016) which reported in February 2017.

In this report it was stated that there was no argument in favor of toxic phenomena related to the presence of barium but that it was appropriate, in particular, to evaluate a possible passage of barium in the skin in subjects who are treated with thermal mud

• by observing, where appropriate, an increase in serum and urinary barium levels in the subjects concerned and
• by measuring a possible depletion of barium in the sludge used. The DGS validated the various recommendations of the Academy and asked, in January 2018, the National Council of Thermal Establishments (CNETH) to implement the recommendations of the Academy.

It will therefore be a prospective before-after interventional study, implementing 15 daily applications of 6 mud poultices made with a clay used as thermal clay and containing appreciable barium levels.

A surveillance will be put in place with the event of suspected event, the volunteer can then be seen by a doctor.

Inclusion Criteria:

• volunteers, healthy (without known and / or treated disease)
• 18 to 30 years old,
• men and women, who can give their informed consent, presenting the elements of cutaneous and general tolerance of sludge applications
• patient affiliated to a social security scheme

Exclusion Criteria:

• subject who can not give informed consent
• pregnant woman ; woman of childbearing years not wishing to have contraception available for the duration of the trial
• subject to a legal protection measure or a judicial review, subject having a known allergy to a heavy metal, a BMI greater than 30
• a characterized contact eczema, an active dermatosis, an acute affection, a disorder of the cutaneous sensitivity, an intolerance to the heat
• heart, kidney or lung disease that may be decompensated with the use of hot products
• a progressive disease (inflammatory, infectious or tumoral) potentially liable to worsen with the application of thermal physical agents