I have seen that it seems to be quite firmly established that butyrate (butyric acid) is a strong inducer of herpes virus reactivation and replication, including EBV, HHV6 and HSV1. Studies: https://www.ncbi.nlm.nih.gov/pubmed/11059774 https://www.ncbi.nlm.nih.gov/pubmed/9753061 https://www.ncbi.nlm.nih.gov/pubmed/17360760 https://www.sciencedirect.com/science/article/pii/0042682286902187 http://grantome.com/grant/NIH/F32-CA165705-03 http://jvi.asm.org/content/88/14/8028.full https://www.ncbi.nlm.nih.gov/pubmed/220786 Butyrate is produced by probiotic colonic bacteria by fermenting fiber and prebiotics. I have also seen a study which I can't find anymore that butyrate produced by colonic bacteria does enter the blood stream. I am wondering if this could be the reason why there are many reports of Herxheimer-type reactions to probiotics and also some reports of getting worse with high intake of fiber. I think high fiber intake (10-20g Psyllium husk) might make me worse, but I have been wondering why this is the case. Could this be an explanation? There is also at least one report on PR from someone who got worse when taking butyrate directly as a supplement (cc: @ebethc). https://forums.phoenixrising.me/index.php?threads/does-butyrate-make-you-sick-at-first.32842/ Usually we think of fiber and probiotics as healthy food choices and intake is encouraged, but maybe it should better be limited in order to lower the amount of butyrate.