Water was the gentlest of the great therapies, and the one that most often helped. Heat loosens muscle and opens what the ancients called pores. Cold checks swelling. Clean water removes dirt that would otherwise sit in a wound. None of that required a correct theory of humors — but humoral language gave bathing a prescription pad.
The Roman sequence
A city bath was a machine for moving the body through temperatures: warm tepidarium, hot caldarium, cold frigidarium, with oiling and scraping (strigil) in between. Celsus turns this civic pleasure into medicine. The fatigued should sit in warmth, descend into tubs, be oiled, and sometimes finish with cold on the face. A near-feverish exhaustion gets a milder hip bath with a little oil in the water — not a blast of heat.
Steam and sweat were thought to thin humors and let them escape. That is wrong as physics and occasionally right as comfort. For joint pain and worry, a warm room is still a treatment.
Cold as a drug
Inflammation, in Celsus’s famous four signs, is red, swollen, hot, and painful. Cooling the surface is a rational reply. Cold cloths for headache, cool rooms for fever, restricted hot baths while the heat of disease is still climbing: the regimen is more nuanced than “ancients boiled the sick.”
Matching heat with heat — plunging a feverish patient into hot water because the disease is hot — also appears. That is the theory overplaying its hand. The better writers watch the patient, not only the slogan.
Ritual immersion in a mikveh is about purity before God, not a prescription for rheumatism. Still, a culture of washing is a medical fact. Levitical isolation of certain skin diseases is another: holiness with a quarantine diagram.
How long, how often
A physician might order morning and evening bathing for weeks. Duration and temperature tracked the diagnosis: longer heat for cold-wet phlegm; shorter, cooler visits for hot-dry bile. Oil after water kept the “moist” in and the skin from cracking — also simply pleasant in a dry climate.