Arnica is a daisy-like plant with yellow flowers. Although high oral doses are toxic, it’s used as a cream to reduce pain, bruises, swelling from injuries, and speed recovery after plastic or dental surgery. But does it actually work? Read on for an evidence-based review of its benefits and side effects.
What Is Arnica?
Arnica (Arnica montana L.), also known as mountain daisy, mountain tobacco, and leopard’s bane, is a plant with orange-yellow flowers that belongs to the same family as sunflowers, dandelions, daisies, and marigolds (Asteraceae) [1, 2].
Arnica grows best at an altitude of 500 – 2,500 meters and is native to the meadows and mountainous regions of Europe, western North America, and northern Asia. Because arnica is endangered in several European countries, its cultivation has increased but the harvesting of wild plants is not allowed [1, 2].
The plant has been used for centuries to reduce the inflammation and pain of [1, 2]:
- Sprains
- Contusions
- Bruises
- Wounds
Today, herbal and homeopathic arnica preparations are applied to the skin for [1, 2]:
- Soft tissue injuries (e.g., smashed fingers)
- Sprains, strains, fractures, and contusions
- Arthritis
- Muscle soreness
- Post-surgical bruises and swelling
Arnica can also be formulated in oral homeopathic pills that are mainly used for [3]:
- Mouth, gum, and throat inflammation
- Headaches
- Diabetic eye damage
- Post-surgical bruises and swelling
- Muscle soreness
The German Commission E has only approved the use of topical arnica (creams, gels, ointments) for injuries, consequences of accidents, and inflammation (mouth and throat, insect bites, boils, veins). The FDA considers oral arnica unsafe due to its toxicity and the Canadian Government prohibits its use as a food ingredient [1, 3].
It’s important not to confound Arnica montana with other plants popularly known as “arnicas”, such as Brazilian (Solidago chilensis and Lychnophora spp.) and Mexican (Heterotheca inuloides) arnicas. They belong to the same family and are also used in traditional medicine, but may have different active compounds and applications [4, 5, 6].
Snapshot of Arnica
Proponents
- Anti-inflammatory
- May Improve arthritis
- Inexpensive
- Easy to apply
- Few side effects when applied to the skin or used as homeopathic pills
Skeptics
- Insufficient evidence for most benefits
- Toxic at high oral doses
- Long-term use can irritate the skin
- Endangered species
Active Components of Arnica
The main active compounds of arnica are sesquiterpene lactones such as helenalin, dihydrohelenalin, and their derivatives [7].
Other components of the plant include [2]:
- Antioxidant compounds (flavonoids, polyphenols, lignans, carotenoids, and chlorogenic acid derivatives) [8, 9, 10, 11]
- Toxic compounds (alkaloids, polyacetylenes, and coumarins) [12, 13]
- Essential oils [14]
- Sugars [15]
Most active compounds are found in the flowers, which are particularly rich in sesquiterpene lactones (0.5 – 0.9%), flavonoids (0.4 – 0.6%), and essential oils (0.2 – 0.5%). The amount of sesquiterpene lactones increases with flower maturity [16, 2].
Seeds are the richest in polyphenols and flavonoids [17].
Roots and underground stems mainly contain essential oils and sugars [18, 15].
The sesquiterpene lactone composition in flowers strongly depends on geography. Flowers from high altitudes mainly contain helenalin, while those from lower meadows are richer in dihydrohelenalin [2, 19].
How Does Herbal Arnica Work?
Inflammation
When arnica’s sesquiterpene lactones penetrate the skin, they block the master inflammation pathway, NF-kb, and proteins that trigger an inflammatory immune response (RelA and NF-AT). This prevents the activation, division, and development of Th immune cells and stops them from releasing inflammatory substances (cytokines) [20, 21, 22, 23].
Arthritis and Bruises
Arnica’s sesquiterpene lactones also block the production of two enzymes (MMP1 and MMP13) that degrade collagen in joint cartilages and blood vessels. By preventing collagen breakdown, arnica may protect joints from arthritis and strengthen blood vessels [24].
Benefits and Uses of Herbal Arnica
Although herbal arnica is not approved by the FDA for any conditions, multiple supplements that contain it are available. Note that supplements generally lack solid clinical research. Regulations set manufacturing standards but don’t guarantee that they are safe or effective. Talk to your doctor before using herbal arnica for any conditions to avoid unexpected interactions.
Herbal arnica is formulated into creams, gels, and ointments. These products contain arnica tinctures or dried flowers (1 – 25%) and their effects rely on arnica’s bioactive components (unlike homeopathic pills). Arnica tea can also be used on the skin, but should not be consumed orally.
Creams or ointments should contain a maximum of 15% arnica oil or 20 – 25% tincture [25].
Possibly Effective for:
1) Pain Relief
Arthritis Pain
In a clinical trial of 79 people with knee arthritis, arnica gel (2.5% arnica extract) applied 2x/day for up to 6 weeks reduced pain, stiffness, and disability. The same gel 3x/day for 3 weeks reduced hand arthritis symptoms as effectively as a 5% ibuprofen gel in a clinical trial on almost 200 people [26, 27].
In rats with arthritis, a high-dose arnica extract (up to 500 mg/kg body weight) reduced joint damage, inflammation, and increased antioxidants [28].
Pain from Traumatic Injuries
A spray for sports injuries with 10% arnica tincture and an anti-inflammatory painkiller (hydroxyethyl salicylate) reduced the pain from ankle distortion and sports injuries in two clinical trials of over 600 people. The combination worked better than either substance alone [29, 30].
Muscle Soreness
In a clinical trial on 20 people, 2.5 g of a 1% arnica flower gel applied every 4 hours after a downhill run reduced muscle soreness better than placebo, but only after 3 days [31].
To sum up, limited evidence suggests that herbal arnica helps relieve pain, especially from arthritis and traumatic injuries. You may try herbal arnica for pain relief if you and your doctor determine that it may help in your case. Importantly, never use herbal arnica in place of what your doctor recommends or prescribes.
Insufficient Evidence for:
2) Bruises
In a clinical trial on 16 people, a 20% arnica extract ointment applied 2x/day for 2 weeks reduced bruising from a laser procedure. It was as effective as a low-dose vitamin K cream and better than placebo [32].
Plastic Surgery
Steroids are most commonly used to reduce bruises and swelling after plastic surgery. But herbal remedies are also gaining popularity [33].
In a clinical trial on over 100 people undergoing nose plastic surgery, a cream with arnica applied 4x/day for 10 days reduced bruises and swelling. However, a 10% arnica ointment failed to improve bruises and swelling after eyelid surgery in a trial on 136 people [34, 35].
3) Wound Healing
In newborn babies, the umbilical cord stump takes up to 2 weeks to dry up and fall off. During this period, special care must be taken due to the risk of infections. In an observational study on over 6,000 babies, a powder containing arnica and echinacea 2x/day prevented infections and helped umbilical cord stumps fall off within only 4 days on average [36].
In a small trial of 2 people with burns, a gel with 0.5% arnica extract and 9.5% stinging nettle extract helped the dead skin tissue fall off sooner and improved wound healing [37].
In an observational study on 50 people with chronic wounds, a powder blend with 0.01% arnica and other herbs was rated effective by 85 – 89% of caregivers. The effects could have been due to other, more abundant components of this blend (mint, sandalwood, and calendula) [38].
Animal and Cell Research (Lack of Evidence):
Researchers are investigating other potential health benefits of herbal arnica. Because the studies are still at the animal and cell stage, there is no evidence that their results will be the same in humans.
4) Infections
In hamsters, an arnica tincture healed skin injuries caused by a parasitic infection (leishmaniasis) better than the more conventional medicine meglumine antimoniate [39].
Arnica extract prevented the growth of several microbes that cause gum disease (Porphyromonas gingivalis, Prevotella spp., Eikenella corrodens, Peptostreptococcus spp., and Actinomyces spp.) in one cellular study [40+].
5) Breathing Function
In Guinea pigs, an arnica complex safely reduced coughing and widened the airways. Its effects were similar to an anti-asthma drug (salbutamol) [41].
6) Skin and Gum Inflammation
Arnica creams are sometimes used to reduce skin inflammation and acne, while dental washes can be used to soothe gum inflammation [25].
Based on cellular studies, arnica blocks the master inflammation pathway NF-kB, reducing the production of many inflammatory substances (IL-1, IL-2, IL-6, IL-8, and TNF-alpha). It also blocks the inflammation-triggering enzyme COX-2 (like NSAIDs such as Advil and Motrin – ibuprofen) and reduces the expression of genes that worsen immune over-activation [25].
However, products with high arnica concentrations used over longer periods of time are more likely to cause skin irritation too, especially in people sensitive to similar plants [25].
7) Arnica Uses in the Food Industry
The food industry uses arnica as a flavoring in [1]:
- Alcoholic and soft drinks
- Frozen dairy desserts
- Candy
- Gelatins
- Puddings
- Baked goods
Limitations and Caveats
Study Results
For most health benefits, studies reported a mix of positive and negative results. Those using homeopathic remedies most frequently showed no differences between the application of arnica and the placebo.
Study Design
A lot of the studies were done on a few people (30 or less), which can produce unreliable results.
Some studies lacked an appropriate placebo control or had no controls at all [26, 42, 43, 44, 45, 36, 46, 47].
The effects of arnica on infections and breathing have only been tested in animal and cell studies. Clinical trials in humans are needed to confirm them.
Study Funding and Conflict of Interest
Several of the studies were funded by companies selling arnica preparations (Bioforce, Boiron, Alpine Pharmaceuticals, Similasan, Cearna) or done by employees of these companies [26, 27, 48, 49, 50, 51, 43].
Side Effects and Safety of Arnica
Oral arnica is very toxic at concentrations higher than those found in foods and homeopathic remedies. The intake of high arnica doses may cause [52, 53, 1]:
- Digestive problems (gastroenteritis, stomachache, vomiting, diarrhea)
- Mood disturbances (drowsiness, nervousness)
- Muscle weakness
- Increased heart rate
- Shortness of breath
- Coma, and even
- Death from heart failure (very high doses)
In an observational study on 86 women who took in different plants to induce abortion, 2 out of 3 women using arnica suffered multiple organ failure [54].
Because the dose of the active compounds in homeopathic preparations is exceptionally low, homeopathic arnica is generally considered to have no risk of toxicity. However, a person who took in a very high amount (100-200 mL) of arnica 30C suffered from blood-stained vomiting and loss of vision. This could have been caused by the alcohol used in the dilutions [55].
Although topical arnica is generally well tolerated, gels and ointments can cause mild to moderate allergic reactions on the skin in people sensitive to its compounds, such as [26+]:
- Local rash
- Itching
- Colored spots
- Dryness
The long-term use of arnica can sensitize the skin and increases the risk of allergic skin reactions.
In an observational study on over 400 people with chronic dermatitis, 5 were allergic to arnica. They all reported applying it on the skin or coming into contact with the plant as hobby-gardeners. A person who repeatedly used arnica tincture for a skin condition (rosacea) developed a contact allergy with blistering [56, 57].
A person who used an undiluted arnica mouthwash (meant to be diluted 1:5 with water) experienced a burning sensation with each rinse and mouth lining injuries [58].
Caution
Importantly, arnica shouldn’t be applied on open wounds or broken, damaged skin to prevent the absorption of too much arnica and its toxicity [1].
People with an allergy to plants of the same family (Asteraceae) such as marigolds and coneflowers should avoid both oral and topical arnica [59].
Although they still can use topical and diluted homeopathic preparations, people with the following conditions should strictly avoid oral arnica [53, 52, 60]:
- Digestive problems
- High heart rate or blood pressure
- Scheduled surgery (due to reduced blood clotting)
Oral arnica (excluding highly diluted homeopathic remedies) is generally considered unsafe, and especially so for pregnant and breastfeeding women. Indeed, a breastfed baby whose mother was drinking tea made from arnica flowers developed anemia due to red blood cell damage [61].
Possible Drug Interactions
Because arnica’s sesquiterpene lactones slow blood clotting, oral arnica may increase the risk of bruises and bleeding in people taking medicines that also reduce blood clotting, such as [60, 62]:
- Painkillers/anti-inflammatories (aspirin, diclofenac, ibuprofen, naproxen)
- Blood thinners (clopidogrel, dalteparin, enoxaparin, heparin, warfarin)
Because homeopathic arnica contains few or no molecules of its active compounds, this interaction may only occur in people taking high-concentration (‘low-potency’) pills, such as 3 – 5 D/X. The interaction is more likely with oral herbal arnica use, which is very rare.
High-dose oral arnica is also not recommended in people using drugs for high blood pressure, since it may reduce their effect [1+].
Forms and Dosage of Arnica
Because both herbal and homeopathic arnica are not approved by the FDA for any conditions, there is no official dose. Users and manufacturers have established unofficial doses based on their experience.
Topical Arnica
Arnica is available as various formulations that can be applied on the skin, such as:
- Tincture: a 1:10 alcoholic extract of arnica flowers
- Oil: essential oil obtained from the distillation of arnica flowers
- Cream
- Gel
- Ointment
- Salve
- Powder
- Tea (2g herb/100 mL water) only for external use. Only people under strict medical supervision may drink the tea, which is considered dangerous.
- Mouth rinse: a 1:10 dilution of arnica extract
- Homeopathic creams, such as Traumeel
Creams, gels, ointments, and salves typically contain 20 – 25% arnica tincture or 15% arnica oil [1].
It is important to buy arnica from a reliable source since it is a protected species in some countries. Unreliable manufacturers may include other plants in their products and fraudulently market them as arnica [25].
Arnica is also included in cosmetic products such as [1, 25]:
- Hair tonics
- Preparations for dandruff and acne
- Perfumes
- Shampoos and bath gels
Oral Arnica
- Homeopathic pills or tablets: typically 5C or 30C
- Less diluted, lower ‘potency’, such as 5D, 6D, 10D or 10X
- More diluted, higher ‘potency’, such as 1M or even 50M
For more on homeopathic arnica, check out this post.
Arnica Cream/Gel
- Tinctures: Dilute 3 – 10x with water and apply to the affected area of the skin or dilute 10x to use as a mouthwash [1+].
- Arthritis: Apply a 2.5% arnica extract gel 2-3x/day for up to 6 weeks [26, 27].
- Sports injuries: Apply a 10% arnica tincture spray 5x/day for 10 days [29].
- Muscle soreness: Apply 2.5 g of a 1% arnica flower gel every 4 hours for 4 days or take 5 arnica 30C pills 2x/day for 4 days [31, 63].
- Bruises due to injuries: Apply 0.25 g of 20% arnica tincture ointment 2x/day for 2 days [32].
- Post-surgical bruises: Apply a cream 4x/day for 10 days or take arnica 1M 3x/day for 3-4 days [35, 64, 47].
Genetics Related to Arnica
Arnica’s helenalin blocks the activation of the pro-inflammatory protein RelA, which is part of the key inflammation pathway NF-kB. It does so by binding to a specific amino acid (Cys38). Variants of the protein with a different amino acid may increase or reduce the effects of arnica by enhancing or preventing the action of helenalin [22, 65].
Arnica also blocks the production of the collagen-degrading enzymes MMP1 and MMP13. Mutations that impact these genes may reduce the effects of arnica on arthritis and bruises [24].
User Experiences
The opinions expressed in this section are solely those of arnica users who may or may not have medical or scientific training. Their reviews do not represent the opinions of SelfHacked. SelfHacked does not endorse any specific product, service, or treatment.
Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice from your doctor or other qualified healthcare providers because of something you have read on SelfHacked. We understand that reading individual, real-life experiences can be a helpful resource, but it is never a substitute for professional medical advice, diagnosis, or treatment from a qualified healthcare provider.
Most people used arnica for bruises, pain, and swelling caused by injuries. Almost all of them reported a fast and strong improvement of the symptoms. People using topical formulations were more satisfied than those taking pills. Only one reviewer who used arnica for sports injuries complained that it didn’t work for him.
Only two users reported adverse effects. One had to wash a cream off immediately due to a burning sensation on the skin and the other one experienced digestive problems after taking the pills.
Similarly, most people using arnica on the skin or as homeopathic pills after plastic surgery reported a fast improvement of bruises and swelling. Only one complained that the pills didn’t work.
Users taking arnica for inflammatory conditions generally reported satisfactory results but were concerned about its possible interaction with blood thinners.
Further Reading
Takeaway
Arnica generally refers to Arnica montana L., also known as mountain daisy, mountain tobacco, or leopard’s bane. It has long been a part of traditional medicine, typically used topically to relieve pain.
Pain relief is also the purported benefit of arnica with the most clinical research behind it. People with arthritis, pain from traumatic injuries, or simple muscle soreness have all experienced an easing of their pain after using topical arnica creams or gels, though multiple consecutive days of application are sometimes required.
Other potential benefits with insufficient evidence include bruising and wound healing. All other reported benefits and uses of arnica have only been investigated in animals or cells so far. Furthermore, many of the clinical studies on arnica suffer from serious design flaws or potential conflicts of interest.
Arnica is highly toxic and should not be consumed by mouth. Side effects of consumption may include vomiting, elevated heart rate, drowsiness, weakness, and shortness of breath. Consuming higher doses may result in coma and even death. Furthermore, the safety profile of arnica is incomplete, especially in pregnant women and children.
