one still has to convince oneself to do it!
- since people are skeptical about it or it doesn't seem to help some, I'd never recommend, just suggest, altho people like Wim Hof propagate it as if it's the one and all.
My sleep lab psychiatrist explains the great effect on me partly with the Gate Theory (the cold limits the pain felt), but also inflammatory things being washed away, and actually there are studies with evidence that cryotherapy balances the cytokines that may be involved in FM, according to the "autoimmune" explanation of FM, which since then I believe may be relevant to my type of FM (as well as others).
I’d agree with the sensory reset idea too tho, since it is also good for any unrest, esp. in my lower back, for the irritation of insect bites (patting not rubbing after of course!). I think cold & then warm bed also helps my circulation and hot & cold flashes to reset. But a main reason is also the 'thought reset', getting my brain down from any racing or ruminating thoughts.
If I were stressed by it, I'd keep it even shorter, 20'', like I usually do at night. Or I'd just do my legs, feet to thighs, and see how that goes. I do actually sometimes just cold wash, e.g. hands to elbows directly, or using a flannel/washcloth. But it's not quite as effective for resetting.
(I also make sure I don't rub the water off my sensitive dry skin after, I pat it off.) Just a reminder: my body does not react favourably at all to long cold, and wind is one of my main triggers. But short sharp is completely different.