I’ve only been told that they do, but never how! How does a cold shower strengthen mucous membranes exactly? Or strengthen your immune system?

Does it really keep you from getting colds or the flu, or if you do still get a cold is it just not as bad as if you took just hot showers?

When I say cold shower I mean just a cold blast of water (like a minute or more) at the end of a warm shower… I think taking all cold showers all the time would just be torture…