Arnica montana L. · herb
Evidence tier: weak
Reduces bruising, swelling, and muscle soreness after injury or sport, topical arnica is one of the best evidenced OTC natural treatments for soft tissue trauma
Helenalin and related sesquiterpene lactones inhibit the transcription factor NF kB in laboratory systems, which would reduce local inflammatory cytokine output. This is a genuine and well characterised in vitro finding and it is the best reason to think arnica could do anything. It is not evidence that it does, and the same reactive sesquiterpene lactone chemistry that produces the NF kB inhibition is also what makes arnica a potent contact allergen and makes it toxic when swallowed. The mechanism explains the harm at least as well as it explains the help.
Weak, and the seed's description of arnica as one of the best evidenced natural treatments for soft tissue trauma is the opposite of what the reviews say. Start with the safety fact that governs everything: the US FDA classifies Arnica montana as an UNSAFE HERB and cautions against taking it orally or applying it to broken skin where absorption can occur, a position NIH LiverTox restates in its Arnica chapter. Ingested arnica is toxic. Memorial Sloan Kettering records that raw herb ingestion can cause gastrointestinal distress, internal bleeding, irregular heartbeat, breathing difficulty and coma, and documents haemolytic anaemia in a 9 day old breastfed infant after the mother drank arnica tea. There is no therapeutic oral dose. On efficacy, all of it is topical or homeopathic and none of it is strong. The systematic review of topical Arnica montana for pain, swelling and bruises found that efficacy at concentrations of 10 percent and below is NOT supported by the available evidence, and the wider literature review is blunt: data on the clinical efficacy of topical arnica are virtually absent, while there have been at least 35 published reports of toxic or allergic skin reactions to it. For the homeopathic preparations, Ernst and Pittler's systematic review of placebo controlled trials (PMID 9820349, eight trials) concluded that most were burdened with severe methodological flaws and that the claim that homeopathic arnica is efficacious beyond a placebo effect is not supported by rigorous clinical trials. LiverTox, reviewing the same field, describes minimal and clinically insignificant degrees of benefit and notes most studies had major methodological flaws. What is left is a plausible mechanism, a long folk tradition, and a real toxicity ceiling.
Topical only, and no authority establishes a standard. The trials that reported any benefit used arnica gel or cream in the region of 20 to 25 percent tincture equivalent applied to intact skin; the systematic review specifically found concentrations at or below 10 percent unsupported. ORAL: none. There is no safe oral dose. The FDA classifies the herb as unsafe for oral use.
Topical: apply arnica gel or cream to bruised or sore areas 2 to 3 times daily. Do not apply to broken skin or open wounds. Avoid long term topical use on the same area.
CRITICAL: TOXIC IF INGESTED, do not swallow. Even small amounts internally can cause serious cardiac effects. For topical use on INTACT skin only, never apply to open wounds, broken skin, or mucous membranes. Allergic contact dermatitis occurs in 1 to 3% of users (Asteraceae/ragweed family). Avoid in ragweed allergy. Not for use on children's skin without dilution. Systemic absorption via broken skin can be toxic, check skin integrity before every application.
Pregnancy: avoid
Breastfeeding: avoid
Active compounds: helenalin, dihydrohelenalin, sesquiterpene lactones, flavonoids, thymol derivatives
Remedies using Arnica · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.