Arnica to accelerate the absorption of a bruise on the skin?

Hematomas are common skin lesions that result in skin discoloration. When there is a sudden strong pressure on the skin (shock, fall, dermatological procedures, etc.), the blood vessels located in the dermis and hypodermis are damaged, allowing blood to flow and infiltrate into the tissues near the skin surface, causing the characteristic black to blue or red to purple color and sensitivity to touch.

Most bruises typically fade within a few days and do not require treatment. However, due to their unsightly and unpleasant nature, some people turn to topical herbal and homeopathic remedies that claim to help reduce discomfort more quickly, mitigate the effects of a bruise, and speed up the healing process, includingarnica.

Aslisted in the European pharmacopoeia, it is said that arnica, one of the most popular remedies, can reduce inflammation and more effectively fade discoloration due to bruises. About thirty research studies have been conducted to support this hypothesis and those showing that arnica could be an effective solution are few and poorly designed. Thus, the current clinical evidence is mixed and inconclusive, while many people are convinced of the effectiveness of this simple approach.

• CAMPBELL A. conducted a single-blind controlled experimental trial evaluating the effect of homeopathic arnica 10M tablets compared to a placebo on bruises, mechanically produced on the forearms of 12 subjects. An oral placebo was administered to the patients before the appearance of the bruises, then 12 and 24 hours after the onset of the bruises. After 72 hours, the same method was followed, replacing the placebo with oral arnica, and bruises were produced on the opposite forearm. It was found that 6 out of the 12 patients had smaller bruises with the arnica treatment and the other 6 showed no difference between the arnica and the placebo. The limitations of this study include the lack of randomization and the too small number of participants not allowing for a satisfactory statistical analysis.

• Two randomized, double-blind, placebo-controlled clinical trials have shown no effect of arnica on the prevention or resolution of post-operative bruising.

  1. IMFELD M. & al. ont réalisé une étude chez 130 patients subissant une ablation de la veine saphène variqueuse. Les patients ont reçu de l'arnica CH5 ou un placebo par voie sublinguale la veille de l'opération et immédiatement après l'opération. Aucune différence significative entre l'arnica et le placebo n'a été constatée en ce qui concerne les hématomes post-opératoires.

  2. ERNST E. & al. ont évalué l'ecchymose chez 62 patients subissant une intervention chirurgicale de la main pour le syndrome du canal carpien. Trois comprimés d'arnica par jour ont été administrés aux patients sept jours avant l'opération et quatorze jours après la chirurgie. Ils ont constaté que l'arnica n’a pas fait mieux que le placebo pour prévenir la formation d’ecchymoses ou pour contribuer à leur réduction post-opératoire.

• Another study confirmed this lack of effectiveness. BAUMANN & al. designed a randomized double-blind trial involving 19 patients with facial telangiectasias. The pre-treatment group (n = 9) applied the arnica gel on one side and the placebo gel on the other side of the face twice a day for two weeks before laser treatment. The post-treatment group followed the same procedure for 2 weeks after the laser treatment. There was no statistically significant difference between topical arnica and the placebo in preventing or accelerating the disappearance of laser-induced bruises.

• However, in a randomized, blind-controlled trial on an oral form of arnica (500 mg), MAAS C. & al found that patients rated bruises as slightly, but not statistically significantly, less severe on the arnica site than on the placebo site.

• In 2010, ALAM M. & co. aimed to determine in a randomized, double-blind controlled trial the effectiveness of topical arnica in reducing the intensity of skin bruises and accelerating their disappearance, induced by pulsed dye laser on the inner arm of volunteers. The researchers reported that a topical application of arnica (20% arnica ointment) reduced bruises more quickly and more effectively than the placebo (petrolatum) when it was applied twice a day for two weeks.

• A 2016 study showed that individuals who took arnica orally after a rhinoplasty (nose surgery) exhibited improved appearance of postoperative bruising.

• A 2017 analysis of over 600 patients from the same year suggested that arnica might reduce eyelid bruising after a rhinoplasty if it is combined with cold compresses. However, a 2021 report from the American Academy of Ophthalmology (AAO) does not support the use of arnica to reduce bruising after oculo-facial surgeries.

In addition to producing inconsistent results, some of the trials exhibit methodological limitations that make the results unreliable. Further, more in-depth research is necessary to assert with certainty that arnica is effective for resolving bruises, as well as determining the appropriate dosages.

By what mechanism?

Although the mechanism is not entirely elucidated, it is suggested that this potential reduction of bruises associated with arnica may be attributed to a vasodilatory effect. However, SCHRÖR K. & al. demonstrated an inhibition in vitro of human platelet function by helenalin and 11α,13- dihydrohelenalin. Similarly, AUDET D. & al. found that oral arnica had no significant effect on various blood coagulation parameters, including bleeding time in vivo.