Woodcut, 1571. Several men and women are bathing in a large open-air bath; some are grouped as couples; two are drinking; and an old man is playing a violin. Balneology is the branch of medical science concerned with the therapeutic value of baths, especially those taken with natural mineral waters. Balneotherapy may involve hot or cold water, massage through moving water, relaxation or stimulation. Many mineral waters at spas are rich in particular minerals (silica, sulfur, selenium, radium) which can be absorbed through the skin.