Asteraceae
Echinacea purpurea
Purple coneflower · Echinacea
- Part used
- rootaerial
- Native range
- Central and eastern North America
- Morphology
- Perennial to a metre and a half with coarse bristly leaves and daisy flowers whose purple rays droop back from a stiff orange-brown central cone.
- Also known as
- Rudbeckia purpurea
What is in it
Evidence
The most intensively studied herb in the world, with the least to show for it. Large well-controlled trials for preventing or shortening the common cold have found little or nothing. Cochrane reviews find, at best, a weak and inconsistent signal that does not survive in the better trials.
Safety
Well tolerated. Allergic reactions occur, particularly in people sensitive to other Asteraceae such as ragweed, and rare anaphylaxis is recorded. Long-term immunological effects are not well characterised.
Interactions: Theoretical concern with immunosuppressants; clinical significance unclear
Regulatory: Widely permitted as a listed medicine ingredient including in Australia.
Historical use
Used by Plains peoples including the Lakota and Cheyenne for snakebite, wounds and sore throat. Taken up by the Eclectic physicians in the late nineteenth century, and heavily promoted in Germany from the 1930s by Gerhard Madaus, who established the modern preparations.
Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.
Worth knowing
Echinacea is the clearest illustration of the preparation problem that makes this whole literature hard to settle.
Trials have used three different species — E. purpurea, E. angustifolia and E. pallida — and different plant parts, and pressed juice, and ethanol extracts, and dried powder. Those are chemically different products. When a body of work like that comes out inconclusive, there is genuinely no way to tell whether the plant does nothing or whether half the trials tested something inert.
What can be said is that the better-controlled and better-powered the trial, the smaller the effect gets — and that is the trajectory of an artefact rather than a discovery.
Nomenclature verified against GBIF backbone taxonomy.