Im a newbie to this thread and am going to chime in as I have been researching probiotics/good gut flora for a few days now. I strongly believe that restoring gut flora is a key to CFS. The link between CFS/Fibromyagia/IBS is very strong. Most CFS/Fibromyalgia sufferers have been shown to have abnormally high levels of bad gut bacteria (SIBO). I think kefir is much superior to yoghurt. It contains many more multiples of probiotics than yoghurt and [There was a post on this thread (rustyj and anniekim) concerned about kefir containing yeast. I did a quick google and came up with these two quotes from separate sites "People with candida albicans may be worried about the yeast's in Kefir. Experience shows that the disease is an imbalance of intestinal flora and friendly bacteria. Yeast helps to rebalance the intestinal flora and fight candida albicans" and "Those of you, who are into kefir drinking for eliminating candida overgrowth, may be scared to death learning that kefir culture contains also candida yeast. Don't panic, all is OK! The candida yeast in kefir is a vicious cannibalistic sister of the infamous Candida albicans". If you google "kefir and yeast allergy" you will find some good information. I am not clear as to how specific your yeast allergy is ie is it related to candida or not? Some posts I found on this google search would address your issues as you know your symptoms best. I think yoghurt contains yeast also but please check this as I do not have a yeast allergy so have not focused on this. Kefir can be made from water also (called water kefir). I am about to make my first batch and start. For those that may need to avoid kefir and yoghurt due to their yeast, other fermented probiotics such as sauerkraut, kombucha tea etc may help a lot too. I have also read from several sources that when taking probioitic pills its best to take the "pearl" form. Look forward to learning more.