No. According to classical literature, Reishi/Ganoderma/Lingzhi is classified as a superior herb. Superior herbs are said to be non-toxic and can be consumed in large quantities and for a long period without any side effects.

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/Ganoderma/Lingzhi is functioning well. These detoxification symptoms will usually go away within a few days of continuous use of Reishi/Ganoderma/Lingzhi.

Furthermore, in American Herbal Pharmacopoeia®'s published monograph on Reishi/Ganoderma/Lingzhi mushrooms, Reishi/Ganoderma/Lingzhi is classified as "Class 1: Herbs that can be safely consumed when used appropriately (McGuffin and others 1997). No side effects were reported in the available clinical literature. Clinicians have reported occasional mild digestive upset and skin rashes in sensitive individuals. These side effects are usually of short duration."

Taking a source of Vitamin C with Reishi/Ganoderma/Lingzhi can help reduce any side effects which may occur upon the initial intake of the herb.