Any time large amounts of pathogens are being killed off in the body quicker than the body is able to eliminate the toxins that the dead pathogens produce, it may cause nausea, vomiting, headaches, diarrhea or other distress, such as excessive tiredness. This is called a Herxheimer reaction and is common when going through a detoxification program and the healing process. Please note that although the experience may not make you feel particularly good for a time, experiencing a Herxheimer reaction is usually a sign that healing is taking place. Other than that there are no side effects except to get well. Having said this, the idea is not to get sicker than you already feel. If one will follow the Three Golden Rules of MMS, as outlined in the MMS Health Recovery Guidebook, a Herxheimer reaction can be greatly minimized and/or avoided all together. On another note, the above mentioned discomforts pale in comparison to some side effects of chemotherapy and other pharmaceuticals.