hiIts callede the herx reaction. it is verry common and the only way to overcome it while taking the probiotics is to plow through it untill it stops after a week or two. The Herxheimer Reaction is a short-term (from days to a few weeks) detoxification reaction in the body. As the body detoxifies, it is not uncommon to experience flu-like symptoms including headache, joint and muscle pain, body aches, sore throat, general malaise, sweating, chills, nausea or other symptoms.This is a normal — and even healthy — reaction that indicates that parasites, fungus, viruses, bacteria or other pathogens are being effectively killed off. The biggest problem with the Herxheimer reaction is that people stop taking the supplement or medication that is causing the reaction, and thus discontinue the very treatment that is helping to make them better. Although the experience may not make you feel particularly good, the Herxheimer Reaction is actually a sign that healing is taking place.What Is The Herxheimer Reaction?The Herxheimer Reaction is an immune system reaction to the toxins (endotoxins) that are released when large amounts of pathogens are being killed off, and the body does not eliminate the toxins quickly enough. Simply stated, it is a reaction that occurs when the body is detoxifying and the released toxins either exacerbate the symptoms being treated or create their own symptoms. The important thing to note is that worsening symptoms do not indicate failure of the treatment in question; in fact, usually just the opposite. Ian