I use kefir on and off. I've just finished a course of anti-biotics, so then i use kefir for a week or two with rice/oat bran etc as a prebiotic.
When i do use it, i have a small glass before bedtime and maybe one in the morning too. I find even yoghurt makes my stomach swell and go hard, and wonder if i have a dairy sensitivity.
Mamapatch is right, moderation is the key.
I am now on the Pau d'arco for my toothache, as i refuse to take another course of Antibiotics . I thought the toothache was coming back, but so far apart from the odd twinge it seems okay.