After 2,000 years, there are still no side effects reported in available literature and clinical studies. However, very sensitive individuals may experience some detoxification symptoms such as mild digestive upset, dizziness, sore bones, and skin rashes during the initial period of intake. This is the excretion of accumulated toxic matters from modern day foods and vigorous activities of the body metabolism. These are all normal signs of recovery and an indication that the medicinal effect of Red Reishi is functioning well. These detoxification symptoms will usually go away within a few days of continuous use of Reishi.