In the meantime, here are a few of the symptoms you might experience during a Die-Off reaction (otherwise known as a Herxheimer reaction). 1  Nausea. 2  Headache, fatigue, dizziness. 3  Swollen glands.  Bloating, gas, constipation or 1  diarrhea. Increased joint or muscle pain.  Elevated heart 1  rate. Chills, cold feeling in your extremities.