The tree fungus known as reishi has a long history of use in China and Japan as a semi-magical healing herb. Presently, reishi is artificially cultivated and widely available in stores that sell herb products.
In people, this mushroom has been suggested for treatment in the following ways: improve resistance to stress; strengthen immunity against colds and other infections; improve mental function; and prevent altitude sickness, asthma, bronchitis, viral hepatitis, cardiovascular disease, ulcers and cancer.
In pets, reishi has been used for the following disorders: internal parasites, demodectic mange, upper respiratory infections, feline leukemia virus infection, feline immunodeficiency virus infection, lack of appetite, post-operative recovery, chemotherapy support, various disorders of aging pets, side effects of corticosteroid therapy, and poisonous mushroom toxicity (as an antidote).
While reishi is marketed as a cure-all for many disorders, no real evidence indicates that reishi is effective for any of these conditions. Contemporary herbalists regard it as an adaptogen, a substance believed to be capable of helping the body to resist stress of all kinds. However, while a great deal of basic scientific research has explored the chemical constituents of reishi, reliable double-blind studies on its effectiveness in treating various disorders are still needed.
The dosage varies with the specific preparation of reishi. Most doctors follow package labeling recommendation.
In people and pets, reishi appears to be extremely safe. Occasional side effects include mild digestive upset, dry mouth, and skin rash. Reishi can “thin” the blood slightly, and therefore should not be combined with drugs such as Coumadin (warfarin) or heparin. Dizziness has been seen in people using reishi for several months. Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established. These guidelines should also be followed for pets.