WebMD says that individuals with auto-immune diseases may experience a worsening of their symptoms as a side-effect of taking cordyceps. The safety of cordyceps during pregnancy and breast-feeding is unknown. Otherwise, WebMD says that cordyceps is possibly safe for most people.
Cordyceps is a fungus that originally grew on caterpillars, according to WebMD. It is now grown in the laboratory. Some individuals take it as a treatment for coughs, respiratory disorders and other health conditions. Others take it as a general tonic to increase energy and stamina. It has been shown to be ineffective in improving athletic stamina, and insufficient evidence has been found to support its use for treatment of any other condition, reports WebMD.