Something shadesong and zarhooie and probably others would appreciate

balneology \bal-nee-AH-luh-jee\ noun: the science of the therapeutic use of baths

Example sentence:
Dori studied balneology in Europe and now applies her knowledge at a spa in California.

Did you know?
"Sure, the hot water feels good. Sure, the massage is nice. But it goes beyond that, advocates say." So wrote Ellen Creager in an article published on February 18, 2001 in the Detroit Free Press. The healing powers of mineral baths have long been touted by advocates like those mentioned by Creager. Though we've had the word "balneology" for just over 120 years, this method of treating aching muscles, joint pain, and skin ailments goes back to ancient times. Proponents of the science of bath therapy created the name "balneology" from the Latin word "balneum" ("bath") and the combining form "-logy" ("science"). Today, some medical institutes in Europe have departments of balneology. Modern "balneologists" impart their knowledge to, or themselves serve as, "balneotherapists," who apply their "balneotherapy" to grateful clients.