Asteraceae

Arnica montana

Arnica · Mountain tobacco · Wolf’s bane

Mixed Serious Protected in several European countries; wild collection restricted

Part used: flower
Native range: Mountain meadows of central and southern Europe
Morphology: A perennial of acid mountain pasture to about sixty centimetres, with a basal rosette and one to three large orange-yellow daisy heads on a sparsely leaved stem.

What is in it

sesquiterpene lactones helenalin, dihydrohelenalin

flavonoids

volatile oil

Evidence

Topical arnica gel has some trial support for bruising and for osteoarthritis pain, in one trial comparable to topical ibuprofen. Homeopathic arnica, which is diluted past the point of containing any, does not outperform placebo.

Safety

Genuinely toxic taken internally. Helenalin causes gastroenteritis, and at higher doses cardiac damage, organ failure and death; fatalities from ingestion of tincture are recorded. Not for use on broken skin, through which absorption is substantial. Contact dermatitis is common with repeated topical use.

Interactions: Additive bleeding risk with anticoagulants when absorbed

Regulatory: Permitted topically. Internal use of material-dose arnica is not permitted.

How the traditions classify it

Galenic A late entrant to European medicine, recorded from the sixteenth century, and used for bruises and trauma.

Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.

Historical use

Used in central European folk practice for bruising, sprains and trauma. Goethe is said to have taken it for angina. Central to homeopathic practice, where it is used at dilutions containing no arnica.

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

Arnica is the plant where a product being homeopathic is genuinely the safer option, which is an unusual thing for this site to say.

Homeopathic arnica is diluted far past the point where any molecule of the plant remains. It does not outperform placebo in trials, and it also cannot poison anyone. Material-dose arnica tincture, sold alongside it and easily confused with it, is toxic if swallowed and has killed people.

Someone who buys the wrong one of two products sitting on the same shelf, both labelled arnica, is in real danger — and the danger runs in the direction opposite to what most people would assume.

Nomenclature verified against GBIF backbone taxonomy.