In russian, the word “обливаться” can be colloquially used to describe a specific recurring activity where you pour a container of cold water on a person with the goal of building up that person’s immunity.
I there an equivalent English idiom/short expression for such an activity?
Okay – here’s another one that might turn up in “niche vocabularies”, even if it’s not used all that often…
cryotherapy – the therapeutic use of cold
…which could reasonably be combined with…
hydrotherapy – the therapeutic use of water
The above link has quite a lengthy definition, including “alternating hot and cold water can stimulate the circulatory system and improve the immune system“, so obviously hydrotherapy does actually cover OP’s intended sense. But combining the two prefixes gives the more specific, and [semi-]credible…
cryohydrotherapy (no dictionary definition, obviously, but there are a few instances of it being used)
Source : Link , Question Author : DVK , Answer Author : FumbleFingers