Arnica
Also known as: Arnica montana, Leopard’s Bane, Mountain Tobacco, Mountain Snuff, Wolf’s Bane
Overview
Arnica is a perennial plant in the Asteraceae family; it is native to Europe and North America. There are multiple species of arnica, but the most commonly used in commercially sold products is Arnica montana, which typically grows at high altitudes (up to 3,000 m altitude). Arnica is mainly applied topically as a gel or a cream, but it can also be found in oral homeopathic preparations, albeit in extremely diluted forms.
Benefits
Arnica contains several different compounds, but the main bioactive constituents are sesquiterpene lactones (STLs) of the helenanolide type (e.g., helenalin, 11-alpha, 13-dihydrohelenanin, and their esters). These compounds mainly work by inhibiting the activation of transcription of nuclear factor kappa B (NF-kB), a key mediator in the inflammatory process. Other mechanisms of action are still not fully understood. In vitro and animal studies suggest that arnica might also have anti-microbial, antioxidant, and immunomodulatory activity. However, the current body of evidence from human (clinical) studies is insufficient.
How it works
While arnica has a long history of use in traditional medicine and homeopathy for diverse conditions (e.g., pain, contusion, wounds, bruising, rheumatism, arthritis in general, and inflammation), the scientific evidence supporting its efficacy remains limited. In regard to post-operative pain, one meta-analysis assessing homeopathic arnica’s effect on pain, bleeding, swelling, and discomfort after minor surgeries (e.g., carpal tunnel surgery, oral-facial, or dental surgery) found no significant effect compared to placebo or other interventions. Arnica is also used topically to treat skin bruising. While the evidence may not align with the marketing claims, one RCT demonstrated that a topical application of arnica was more effective than petrolatum ointment or a mixture of 1% vitamin K and 0.3% retinol in reducing laser-induced skin bruising. However, larger studies are essential to validate and establish the consistency of this effect. Regarding arnica’s effectiveness in relieving osteoarthritis symptoms, positive outcomes have been observed, particularly for hand and knee osteoarthritis.
Side effects
When applied topically for osteoarthritis, arnica was seen to be effective at a concentration of 50 grams of tincture per 100 grams of product (i.e., 50 grams of a 1:20 arnica extract mixed into 100 grams of a gel). In one study, a topical gel containing the equivalent of 10 mg of dried flowering herb was used to reduce delayed onset muscle soreness (DOMS) after intense exercise. The gel was applied immediately after exercise and then every 4 hours for 4 consecutive days. Arnica homeopathic preparations may contain various dilutions of arnica (e.g., 6C, 30C). Due to the lack of strong scientific evidence supporting the use of homeopathic preparations, an effective dosage has not yet been established.
Dosage
The oral use of arnica is currently limited to homeopathic preparations, due to a certain degree of toxicity being observed in past studies when arnica was taken orally in higher dosages. Notably, one randomized controlled trial (RCT) reported side effects such as dry mouth, headaches, drowsiness, and lethargy with the use of homeopathic arnica tablets, though causality could not be definitively established. Although infrequent, topical applications of arnica may lead to skin irritation or contact dermatitis, emphasizing the importance of conducting a patch test before applying it to larger areas. Moreover, arnica should not be applied to broken skin. Finally, due to a lack of data, arnica is not recommended during pregnancy or breastfeeding.
FAQs
What is arnica?
Arnica is a perennial plant in the Asteraceae family; it is native to Europe and North America. There are multiple species of arnica, but the most commonly used in commercially sold products is Arnica montana, which typically grows at high altitudes (up to 3,000 m altitude). Arnica is mainly applied topically as a gel or a cream, but it can also be found in oral homeopathic preparations, albeit in extremely diluted forms.
What are arnica’s main benefits?
While arnica has a long history of use in traditional medicine and homeopathy for diverse conditions (e.g., pain, contusion, wounds, bruising, rheumatism, arthritis in general, and inflammation), the scientific evidence supporting its efficacy remains limited. In regard to post-operative pain, one meta-analysis assessing homeopathic arnica’s effect on pain, bleeding, swelling, and discomfort after minor surgeries (e.g., carpal tunnel surgery, oral-facial, or dental surgery) found no significant effect compared to placebo or other interventions. Arnica is also used topically to treat skin bruising. While the evidence may not align with the marketing claims, one RCT demonstrated that a topical application of arnica was more effective than petrolatum ointment or a mixture of 1% vitamin K and 0.3% retinol in reducing laser-induced skin bruising. However, larger studies are essential to validate and establish the consistency of this effect. Regarding arnica’s effectiveness in relieving osteoarthritis symptoms, positive outcomes have been observed, particularly for hand and knee osteoarthritis.
What are arnica’s main drawbacks?
The oral use of arnica is currently limited to homeopathic preparations, due to a certain degree of toxicity being observed in past studies when arnica was taken orally in higher dosages. Notably, one randomized controlled trial (RCT) reported side effects such as dry mouth, headaches, drowsiness, and lethargy with the use of homeopathic arnica tablets, though causality could not be definitively established. Although infrequent, topical applications of arnica may lead to skin irritation or contact dermatitis, emphasizing the importance of conducting a patch test before applying it to larger areas. Moreover, arnica should not be applied to broken skin. Finally, due to a lack of data, arnica is not recommended during pregnancy or breastfeeding.
How does arnica work?
Arnica contains several different compounds, but the main bioactive constituents are sesquiterpene lactones (STLs) of the helenanolide type (e.g., helenalin, 11-alpha, 13-dihydrohelenanin, and their esters). These compounds mainly work by inhibiting the activation of transcription of nuclear factor kappa B (NF-kB), a key mediator in the inflammatory process. Other mechanisms of action are still not fully understood. In vitro and animal studies suggest that arnica might also have anti-microbial, antioxidant, and immunomodulatory activity. However, the current body of evidence from human (clinical) studies is insufficient.
Is arnica effective in relieving symptoms of osteoarthritis?
In one RCT involving individuals with hand osteoarthritis, arnica gel (50 grams of tincture per 100 grams of gel, three times daily) was comparable to ibuprofen 5% gel in improving hand functional capacity, pain intensity, number of painful joints, and duration and severity of morning stiffness. Similar results were reported in another non-randomized study using a fresh-plant tincture of arnica twice daily for knee osteoarthritis. However, it’s important to note that neither study included a placebo comparison.
Is arnica effective in relieving exercise-induced muscle pain?
One RCT assessed the effect of arnica gel (1 gram of gel containing Arnica montana tincture equivalent to 10 mg of dry flowering herb) on delayed onset muscle soreness (DOMS) and performance in well-trained males subjected to intense eccentric exercise. Although arnica did not show any significant effect on performance, or on blood markers of muscle damage (i.e., creatine kinase, myoglobin, high-sensitivity C-reactive protein, interleukin 1-beta, interleukin-6, tumor necrosis factor-alpha), it did reduce pain 72 hours after exercise compared to the placebo group.
