European arnica

The principal bioactive sesquiterpene lactone of the flowers. Its exocyclic α-methylene-γ-butyrolactone group alkylates cysteine residues, inhibiting the DNA binding of transcription factors NF-κB and AP-1, which accounts for the strong anti-inflammatory action. It also underlies the herb's contact-allergenic potential and its toxicity when taken internally.

A close congener of helenalin, present together with their short-chain carboxylic-acid esters (acetate, isobutyrate, methacrylate, tiglinate). Contributes analgesic and anti-inflammatory activity and, like helenalin, inhibits NF-κB signalling, though it is generally somewhat less cytotoxic.

Antioxidant and mild anti-inflammatory constituents that scavenge free radicals and may contribute to capillary-protective and wound-supporting effects attributed to arnica preparations.

Polyphenolic antioxidants that add to the free-radical-scavenging and anti-inflammatory profile of the extract.

Faradiol monoesters are recognised anti-inflammatory/anti-oedematous principles that reduce experimentally induced skin oedema, supporting the traditional topical use for bruises and swelling.

Provides mild antimicrobial and preservative activity and the aromatic character of the flower; a minor contributor to overall pharmacology.

Minor phenolic constituents with antioxidant activity; their presence is one theoretical basis cited for caution with anticoagulant drugs.

A tincture of the dried flower heads (commonly DER around 1:10 in ethanol, or an equivalent gel) is applied to unbroken skin over bruises, sprains, myalgia and osteoarthritic joints. Warning: Arnica is toxic if swallowed — undiluted preparations must not be taken internally. Do not apply to open wounds, broken skin or mucous membranes, and discontinue if dermatitis develops, as sesquiterpene lactones are potent contact allergens.

Flowers are macerated in a fixed oil (or incorporated into an ointment base) and used externally for massage over intact skin for muscular aches and bruising. Same external-use-only and allergy cautions apply.

A diluted tincture (typically about 1 part tincture to 3-10 parts water) is used to soak a cloth for a cold compress on bruises and sprains over unbroken skin.

Only highly diluted homeopathic potencies (e.g. 6C/30C) are taken orally; these contain negligible amounts of the toxic sesquiterpene lactones. Crude/material-dose oral arnica should never be used because of the risk of gastroenteritis, cardiotoxicity and mucosal irritation.

In patients with osteoarthritis of the interphalangeal hand joints, a topical arnica tincture gel was compared with 5% ibuprofen gel over 21 days. There were no significant differences between groups in pain relief or hand-function improvement, indicating that this arnica preparation was not inferior to ibuprofen gel for this indication.

Standardised pulsed-dye-laser bruises on volunteers' inner arms were treated twice daily for two weeks with topical 20% arnica, vitamin K formulations or petrolatum. Topical 20% arnica reduced bruising significantly more than placebo and more than low-concentration vitamin K, supporting a role in accelerating bruise resolution.

Twice-daily application of an arnica tincture gel for six weeks in patients with mild-to-moderate knee osteoarthritis produced significant improvements in pain, stiffness and function scores, with good tolerability. As an open uncontrolled trial the findings are suggestive rather than confirmatory.

Records the long-standing central-European folk use of Arnica montana (Fallkraut, Wohlverleih) as an external remedy for bruises, sprains and traumatic injury, and warns of its toxicity when taken internally.

Official monograph approving arnica flower for external use in injury and inflammation from accidents (bruises, sprains, rheumatic muscle and joint complaints), while explicitly cautioning against internal use and against application to broken skin.