Common Tansy Tanacetum vulgare contains a volatile oil, tanacetin or
"oil of tansy," which is extremely variable in its chemical composition, but
usually contains large amounts of thujone, a monoterpene ketone present in many
essential oils. It can cause convulsions and psychotic effects in people.
Because of its strong taste and smell it is rarely touched by animals.
Several related plants also containing thujone have been used in herbal
medicine, including Yarrow (Achillea millefolium), and various Sagebrush
and Wormwood species (Artemisia spp.).1 Habitual abuse of the
wormwood spirit absinthe was described in the 19th and 20th centuries as a cause
for the mental disorder "absinthism" including the symptoms hallucinations,
sleeplessness and convulsions.2 Plants containing thujone should be
regarded with extreme caution.
Recent research studies have revealed that thujone works by blocking brain
receptors for gamma-aminobutyric acid, or GABA. Without access to GABA, which
is a natural inhibitor of nerve impulses, neurons fire too easily and their
signaling goes out of control leading to epileptic