Reishi mushroom is a fungus that some people describe as tough and woody with a bitter taste. The fruiting body (above-ground part) and mycelium (filaments connecting a group of mushrooms) are used as medicine.
Reishi mushroom is used for boosting the immune system; viral infections such as the flu (influenza), swine flu, and avian flu; lung conditions including asthma and bronchitis; heart disease and contributing conditions such as high blood pressure and high cholesterol; kidney disease; cancer; and liver disease. It is also used for HIV/AIDS, altitude sickness, chronic fatigue syndrome (CFS), trouble sleeping (insomnia), stomach ulcers, poisoning, and herpes pain. Other uses include reducing stress and preventing fatigue.
In combination with other herbs, reishi mushroom is used to treat prostate cancer.
Reishi mushroom contains chemicals that seem to have a variety of potentially beneficial effects, including activity against tumors (cancer) and beneficial effects on the immune system.