Arnica – the facts the studies have extracted

The Irish Times
Health Supplement, p. 13
16 December 2008

DOES IT WORK? Arnica and bruises

Arnica remedies are popularly recommended to reduce pain and swelling from bruises, sprains and aches. The remedies can be made from a number of species belonging to the genus Arnica, which is a member of the sunflower family. The Latin name ‘arnica’ means lamb’s skin and refers to the soft, hairy leaves of the plant.

The flowering heads of the plants are extracted using alcohol and water to give a tincture. Arnica herbal ointments and gels typically contain 25-50 percent of this extract and should always be used topically on unbroken skin. In contrast, homeopathic arnica preparations are diluted repeatedly (sometimes by several hundred-fold), leaving tiny amounts of plant extract, if any. Such homeopathic arnica products are usually taken orally and should be clearly distinguished from the topical preparations.

Evidence from studies

Several laboratory studies have found that arnica extracts contain chemicals which reduce inflammation. However, very few studies have examined the herbal ointments or gels in humans. In one study, a group of patients with knee osteoarthritis used arnica gel twice daily. After three weeks, their knee pain and stiffness was significantly reduced. However, no comparison group was used in this study which limits its value.

The same research team recently published another trial in which arnica gel was compared with ibuprofen gel. Such anti-inflammatory gels are often used by patients with osteoarthritis. In this study, people with hand osteoarthritis found the two gels to be equally effective in reducing pain and improving hand function.

In contrast with the few studies of topical herbal arnica, several randomized, double-blind studies have examined the effect of homeopathic arnica on pain and bruising. In one, 29 patients undergoing cosmetic surgery to remove wrinkles took either oral homeopathic arnica or placebo. No significant differences in bruising were observed by the patients or their healthcare professionals. In another controlled study, 64 patients underwent carpal tunnel surgery and took either homeopathic arnica or placebo. Severity of pain and bruising did not differ between the two groups. Another study examined almost 100 women undergoing hysterectomy who took either oral homeopathic arnica or placebo on the day before surgery and for three days after surgery. No significant differences were found between the two groups for postoperative pain, infection rate or use of other pain medications. In a large study, over 500 runners took either homeopathic arnica or placebo the night before a race and for four days afterwards. The two groups did not differ in muscle soreness or pain. Other high-quality studies have been conducted and similarly found no benefit from homeopathic arnica.

Problematic aspects

Arnica plant material or remedies containing large amounts of extract should not be taken orally. The plant contains a toxin called ‘helenalin’ which causes heart palpitations, vomiting, drowsiness and shortness of breath in adults. Some serious and even fatal cases of poisoning have occurred when large amounts of helenalin have been ingested. Helenalin is toxic to the heart and therefore arnica plants and herbal remedies should not be ingested.

The topical ointments and gels can cause itching and rashes in some people. Those allergic to the daisy family are particularly sensitive. These products should not be used on broken skin.

Homeopathic arnica contains little or no plant material and has not caused adverse effects.


It is very important to identify whether the arnica preparation is homeopathic or contains a significant amount of plant material. Although homeopathic arnica is commonly recommended for bruises, sprains and swelling, several high-quality studies have shown that it is no more effective than placebo. The lack of benefit is to be expected given that homeopathic remedies are so diluted they contain little or no active ingredient. It is possible that topical ointments and gels made from extracts of arnica may have some benefit for pain and swelling. However, very little research has been published in this area. Arnica gel might be worth considering if other treatments have not been effective or cause adverse effects.

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