I am really interested in the "healing crisis". You are right - that bout of "flu" was a classic healing crisis in my experience. The same thing happened to me when I gave up dairy 18 years ago. What is so difficult is to distinguish between a healing crisis and a reaction that could turn into a serious health issue. I would really like to perservere with kefir but I have some bad pains in new places that have popped up since kefir and the constipation is a tricky issue.
Something very specific happened after the "flu" I thought I was doing ok. After a month I did a better BM ( I rely on Oxypowder for BM's and I was taking less) and then wham! everything went wrong.
I am going to do some more research. I have such bad food reactions now since stopping kefir (and it's been 10 days or more) I might just as well drink it again. Probably just the whey though.