Tansy is an herb with a long and interesting history. It is no longer recommended for internal use because it contains thujone, a highly toxic compound that can cause, even in very small doses, vomiting, headaches, and even death.

Here are 5 things to know about tansy:

• Tansy is highly effective for repelling ants, mice, lice, moths, and other plant and people pests (such as mosquitoes). It is often planted with cucumbers, squash, cabbage, roses, and various berries to help protect them from pests. It is also used to repel cockroaches, bedbugs, and tics.
• Tansy is highly toxic to internal parasites and for centuries has been used to treat worms, including roundworm and threadworm.
• In the 19th century, in Irish folklore traditions, it was suggested that taking a bath of a solution of tansy and salts would help to cure joint pain.
• Blue tansy (Tanacetum annuum) is often confused with common tansy (Tanacetum vulgare). Blue tansy is a commonly used dark blue essential oil with a completely different chemical profile and containing none of the compounds that are known to be toxic in common tansy. Blue tansy essential oil is used to calm, improve sleep, and help reduce anxiety.
• Many of the traditional applications of tansy have been discredited by today’s science, even so, tansy remains a component of some medicines and is listed by the United States Pharmacopeia as a treatment for fevers, feverish colds, and jaundice.

Find out more about Tansy (Ai Ju).