What, if anything, is Arnica Cream?

What are the actual therapeutic effects of one of the most meme’d parts of the Depp/Heard trial?

I’ll admit that I am not much of a passive viewer of the Depp/Heard trial. It reflects so much of what we see happening within our culture at large, so I can’t help but become slightly captivated with how the public is reacting to the ongoing procedure.

If anyone has been keeping track of the trial, you’d be well aware of the level of memeing¹ that this trial has reached, with such feats including reenactments of Amber Heard’s direct using cats, or Tik Tok videos mimicking Heard’s exaggerated expressions when explaining how her dog stepped on a bee².

But aside from all of the Amber Heard memes, one of the most “memeified” parts of this trial occurred right at the beginning, when Amber Heard’s attorney Elaine Bredehoft continuously mispronounced the word “Arnica”- with an “r & n”, as “Amica”- with an “m”.

I’ve never heard of Arnica cream before- and I’m sure most of the viewers of this trial have not either. But the few people commenting on Arnica cream mentioned that it is supposed to reduce bruising (Amber Heard supposedly used Arnica cream to cover up bruising and to possibly use it to help accelerate healing). A few people also commented that it was pseudoscience since most Arnica products are homeopathic in nature.

Because of how popular this meme has become, I suppose it would be a little interesting to dive into some culturally (albeit of the “popular” variety) relevant topics and look a bit into what Arnica cream actually is.

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What, if anything, is Homeopathy?

Before we begin, we should briefly define homeopathy.

Depending on which circles you run in homeopathy may be seen as an effective natural remedy or a form of pseudoscience. Note that the intent here is not to choose a side, but to understand that there are plenty of preconceived notions about homeopathy.

Biases aside, homeopathy is an alternative form of medicine that typically depends upon two principles:

• “Like cures like”

• “The rule of minimal dosing”

The NIH provides their own definition and information below, and additional information can be found here³:

I won’t discuss the first principle, as it usually is not referenced much in regards to homeopathic remedies. The more important idea is the second principle of minimal dosing. I won’t dive too deep into the ideas behind the low dosing used in various homeopathic products⁴, but just understand that the process takes a therapeutic compound and puts it through successive dilutions.

The Homeopathic Pharmacopoeia of the US (HPUS) usually labels homeopathic products with said dilution. For example, an “X” and “C” Roman numeral notation indications a 1/10 and 1/100 dilution, respectively. The number in front of the Roman numeral indicates how many serial dilutions occurred using the therapeutic agent. As a reference: if a product indicates a “10C HPUS” notation it means that the therapeutic agent underwent 10 successive 1/100 dilutions.

Another way of putting it- the original concentration of the therapeutic agent should be diluted down to (1/100)^10 or 0.00000000000000000001th of the original concentration. From that, we can see how the actual agent may be nearly nonexistent in the end product.

Homeopathy tends to get a bad rep for it’s infinitesimally low level of therapeutic compounds, and thus tends to be associated with nothing more than a placebo effect. However what we may find out is that homeopathy may be an archaic term, and that many homeopathic products may not follow these typical principles of homeopathy.

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What, if anything, is Arnica?

Although the trial referenced Arnica (well, “Amica”) cream specifically, Arnica itself is actually a genus of plants that comes from the Asteraceae family which includes tens of thousands of flowering plants such as sunflowers and daisies.

The Arnica genus comprises a few dozen perennial herbs and the flower heads are typically yellow. The most important species pharmaceutical-wise is the mountain Arnica (Arnica montana), which has been the most widely utilized of the Arnica in naturopathic and homeopathic medicine. As an herbal remedy, Arnica has been used extensively for centuries in both Europe and America.

An image of mountain Arnica (Arnica montana).

Various over-the-counter products are available containing Arnica including ingestible tablets, oils, and the now famous Arnica creams.

Various Arnica-containing products. From left to right: gel, cream, tablet/pills, and oil.

Because Arnica products are usually associated with homeopathy, they usually contain serial dilutions of the intended therapeutic agent.

Arnica cream products usually have a “1X HPUS” notation, and thus is a 1/10 dilution of the original concentration. Arnica tablets are usually notated with “30C HPUS”. I won’t calculate that, but that’s essentially a 1/100 dilution done 30 times- I suggest you all figure that calculation out on your own!

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What, if any, are the therapeutic compounds found in Arnica?

Arnica (most notably mountain Arnica) is comprised of nearly 150 therapeutically active agents, many of which are typically found in other therapeutic plants and herbs (Kriplani, et. al.⁵):

One hundred and fifty therapeutically active substances are present in A. montana plant, i.e. sesquiterpene lactones, i.e. helenalin,11a,13-dihydohelenalin and their short-chain carbonic acid esters (0.3–1% of dry weight in the flower heads, 0.1–0.5% in leaves), flavonoids (0.6–1.7%) by micellar electrokinetic capillary chromatography[26] in the form of flavonoid glycosides, flavonoid glucuronides and flavonoid aglycones; essential oils, composed thoroughly of fatty acids, thymol derivatives, monoterpenes and sesquiterpene. Other constituents of A. montana are carotenoids; diterpenes; arnidiol (a triterpene); pyrrolizidine alkaloids (tussilagine and isotussilagine)[27]; polyacetylenes; coumarins (umbelliferone and scopoletin); phenolic acids (chlorogenic acid, caffeic acid and cynarin, 1.0–2.2%)[26]; lignans; dicaffeoyl quinic derivatives (1,3- 3,5 and 4,5 dicaffeoyl quinic acids); and oligosaccharides.[22]

Possibly the most important agents within Arnica are the sesquiterpene lactones, which are found ubiquitously in all facets of the plant. For us humans, we tend to get the largest amount of dietary sesquiterpene lactones through lettuce and chicory.

Sesquiterpene lactones have been researched for quite some time for their anticarcinogenic and anti-inflammatory properties. However, there have been plenty of other diseases being researched using sesquiterpene lactones (Chadwick, et. al.⁶):

Studies into the health benefits of sesquiterpene lactones tend to focus on their anti-tumor potential [3,31,36,50,51], as some of the SLs have been found to show enough potential to enter clinical trials [2]. Fewer papers look at other applications in disease treatment, and at prospective health benefits. Despite this, work shows that there is much potential for sesquiterpene lactones in the treatment of cardiovascular diseases [7,33] and their use as antimalarials and are responsible for a range of other effects such as prevention of neurodegeneration, antimigraine activity, analgesic and sedative activities and treatment of ailments such as diarrhoea, flu, and burns [1,6,52–54]. 

A few sesquiterpene lactones are indicated below:

From Keplani, et. al. Sesquiterpene lactones and its derivatives. Helenalin may be the most extensively studied of the Arnica-derived lactones.

One target of these lactones appears to be a protein complex called nuclear factor κB (NF-κB). In short, NF-κB comprises a family of transcription factors involved with immune and inflammatory responses (Liu, et. al.⁷):

The transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory responses. NF-κB induces the expression of various pro-inflammatory genes, including those encoding cytokines and chemokines, and also participates in inflammasome regulation. In addition, NF-κB plays a critical role in regulating the survival, activation and differentiation of innate immune cells and inflammatory T cells. Consequently, deregulated NF-κB activation contributes to the pathogenic processes of various inflammatory diseases. 

It is likely through the inhibition of NF-κB and the following cascade of events that inflammatory and tumor proliferation is inhibited.

There are many other possible targets as well, and it appears that another target is the protein complex tumor necrosis factor α (TNF-α) (Smith, et. al.⁸):

The Lychnophora passerina (a Brazilian Arnica) crude ethanolic extract, and its ethyl acetate and methanolic fractions, reversed the lipopolysaccharides/interferon gamma-induced nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α) production in J774.A1 macrophages [49]. The crude extract and fractions also increased the production of the anti-inflammatory cytokine, interleukin (IL)-10 [49]. Further, an ointment containing either 10% of the crude ethanolic extract or 20% of the fractions showed a similar effect to that of diclofenac in the carrageenan-induced paw edema mice model [49]. The anti-inflammatory activities of Arnica were also determined in human umbilical vein endothelial cells stimulated with TNF-α [50]. Treatment with Arnica diminished the expression of the intracellular cell adhesion molecule (ICAM-1) induced by TNF-α in the endothelial cells [50] and increased the anti-inflammatory macrophage population compared to pro-inflammatory macrophages in mice with injured skeletal muscles.

So it is likely through these pathways that Arnica aids in swelling and bruising, as well as other clinically relevant diseases. By inhibiting inflammatory pathways Arnica may limit the level of inflammation taking place, although it’s worth noting that extensive inflammatory inhibition may reduce the healing process. Arnica may also serve as an immunostimulatory agent which may accelerate healing. It could be that a complex response from the various therapeutic compounds may provide a balance of reduced swelling as well as a faster healing process.

And like with many naturopathic remedies, various compounds derived from Arnica are continuously being looked at for their therapeutic properties, including other terpenes and flavonoids such as Quercetin.

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What, if any, clinical studies are there involving Arnica?

So I have mentioned that homeopathic medicine follows a path of minimal dosing and is considered one of the main faults of homeopathic medicine. For all intents and purposes, this creates a bit of difficulty in assessing clinical studies utilizing Arnica.

Irrespective of whether we consider homeopathic medicine to be pseudoscience or effective, let’s presume that dosing is a pivotal aspect of a product’s effectiveness. We would then have to consider that clinical trials and dosing is heavily important to Arnica’s effectiveness in clinical studies.

Several studies are not necessarily intended to show the effectiveness of Arnica, but instead may be evaluated on its ability to discredit the field of homeopathy specifically. However, we must take into account that some studies may also be setup to prove the effectiveness of Arnica homeopathic medicine. Either way, Arnica studies provide mixed results and plenty of heterogeneity.

One meta-analysis conducted by Gaertner, et. al.⁹ looked at the effects of homeopathic Arnica as a treatment/preventative pain option for surgery. When looking at over 18 studies comparing Arnica to Placebo the researchers noted a very small effect.

From Gaertner, et. al. Fig. 2. A Forest plot showing the results of 18 clinical studies in regards to Arnica.

It’s worth noting that out of the 18 studies comparing Arnica to Placebo, 16 of them were preventative and only 2 used Arnica as a treatment option. There was also a heavy risk of bias (i.e. Macedo, Pincent) and several studies used doses up to (or as low as?) 200C Arnica (Erkan). Most studies also looked at Arnica for teeth removal/extracts and only one study (Sorrentino, et. al.) looked at Arnica in regards to treatment for mastectomy. It is likely that plenty of factors contribute to the results seen and it is rather difficult to compare each study to one another.

One systematic review by Ernst, E. & Pittler, M. H.¹⁰ looked at 8 clinical trials involving Arnica use and suggested that there was no significant evidence of Arnica’s effectiveness compared to placebo.

From Ernst, E. & Pittler, M. H. Table 1. Key data from 8 clinical studies with Arnica and a Jadad Score on the far right. A Jadad Score provides a number based on the strength of a study’s methodology with 0 or 1 indicating very poor methodology while a 5 indicates superior methodology.

The researchers do provide some important insight as to why this may be occurring (emphasis mine on an interesting comment):

The existing studies could be severely flawed and therefore produce a misleading result. The trials certainly are burdened with a multitude of methodological limitations. Small sample size and lack of test statistics are frequent and obvious ones. However, such drawbacks would be likely to create a false-positive rather than a false-negative result.

Arnica could have been applied wrongly. Homeopaths do not treat a specific condition but rather the whole human being. Thus, it is not strictly according to the teaching of Hahnemann (the "inventor" of homeopathy) to use arnica for trauma much like an allopathic drug. There are, however, exceptions to this rule, and arnica is certainly one of them. The above quotations demonstrate that arnica is used for the conditions for which it was tested in the trials reviewed here.

Therefore, the hypothesis that homeopathic arnica is, in fact, not effective beyond a placebo effect must be considered. It is not possible to "prove a negative" with these data. It is, however, possible to comment on the most likely explanation of the overall result of this systematic review.

Overall, a majority of Arnica studies are far too heterogeneous to produce consistent results, as plenty of other variables and differences in methodology are likely to confound the various studies regarding Arnica.

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Who, if anybody, should use Arnica?

Aside from the extensive memeing that has sprouted up from the Depp/Heard trial, many people may have become far more interested in figuring out what exactly Arnica cream is, and whether it is an effective treatment option for bruising and swelling.

This article is not intended to suggest whether people should use Arnica, but what we may take away is the discrepancy between homeopathic and allopathic medicine in regards to Arnica, as bolded in the above excerpt.

Arnica is considered to be a homeopathic remedy, but that notation may depend upon the product. Arnica cream is hardly diluted while Arnica tablets are diluted way above (or below?) Avogadro's number¹¹. In essence, some Arnica products may be considered homeopathic in nature (i.e. tablets) while some may be considered more allopathic (i.e. creams, gels).

Because Arnica products don’t necessarily follow the intended principles of homeopathy, it may not be appropriate to brush off all Arnica products as junk science. Instead- for those of us who believe in the concept of a therapeutic dose- we may be more inclined to examine Arnica based upon its dosing and route of administration.

Arnica creams and gels, which are more more concentrated and locally administered, may actually provide some benefit to minor swelling, cuts, and bruises¹². The nearly nonexistent level of actual Arnica found in Arnica tablets which are administered orally may actually be providing a placebo effect more than anything therapeutic when examined from a non-homeopathic perspective.

But what may be more important is the extensive studies looking into the various compounds extracted from Arnica.

Many of our ancestors were right in their utilization of their surroundings; nature provides a plethora of its own therapeutic agents. Ingestion or topical application of these plants are likely to have provided some therapeutic benefits.

However, it is only now through modern scientific techniques can we extract and analyze plant-derived compounds for their therapeutic composition; it’s how we can tell that the sesquiterpene lactones, flavonoids, and other polysaccharides derived from Arnica are likely to provide some benefit.

Rather than dismiss products under the guise of junk science, it may be more important to bring many of these products into the modern context, and examine them through the lens of modern techniques in order to properly evaluate their therapeutic effects.

So for now, Arnica cream may not be just a meme created from a possible handwriting slip-up, but may be a product with some possible benefit.

But like with anything, always make sure to do your own research. And maybe make sure you can read your own handwriting before you stand in front of a trial being watched by millions worldwide.

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For those who may not have caught on (or for those who somehow made it this far), Amber Heard’s Attorney Elaine Bredehoft also has a habit of using the phrase “what, if anything…” as an attempt to avoid “leading the witness”. Leading the witness is when an attorney asks a question to a witness that presupposes the answer. So instead of asking, “What happened on Tuesday?”, hoping a witness would describe the events that happened that day, a leading question may say, “what, if anything, did you do in that ice cream shop on Tuesday?”, which points a witness to what you would specifically want to hear from him/her. It’s a wink and a nudge by an attorney to which direction you would like the witness to go down.

Note: OK, that may not have been a good example above, but most leading questions typically can be answered with a “yes” or “no” response.

1. I will not define what a “meme” is since I think we all should be fully aware of what these things are now. If not, please refer to your niece, nephew, or anyone of younger stature that is more than likely to refer to you as a “boomer”.

2. Unfortunately, many of these videos and memes have been removed from Tik Tok. You’ll notice that there has been quite a bit of censorship and outcry by news outlets to create a nanny state for making light of the trial.

3. Keep in mind that although the NIH has dedicated departments to examine alternative forms of medicine, it may not be doing so with the intent to further scientific endeavors within these fields, but may be more focused on discrediting their veracity. Irrespective of our own biases, we should keep in mind that the NIH itself may (or really are) working with their own biases at play.

4. The idea behind minimal dosing is that there is a dose at which the treatment can stimulate the healing process without leading to the adverse reactions usually seen with conventional medicine. This concept is intended to create a more gentle response to the treatment. Successive dilutions are based on the idea of “potentiation”, in which diluting a substance and vigorously shaking the dilution makes this new solution “potent”. This concept usually depends on the idea that more is at play than the chemical makeup of a drug, such as a possible “essence” that permeates through all successive dilutions.

5. Priyanka Kriplani, Kumar Guarve, Uttam S Baghael, Arnica montana L. – a plant of healing: review, Journal of Pharmacy and Pharmacology, Volume 69, Issue 8, August 2017, Pages 925–945, https://doi.org/10.1111/jphp.12724

*For anyone who wants to read more on Arnica, I would suggest this review as it appears to be the most extensive in its content.

6. Chadwick, M., Trewin, H., Gawthrop, F., & Wagstaff, C. (2013). Sesquiterpenoids lactones: benefits to plants and people. International journal of molecular sciences, 14(6), 12780–12805. https://doi.org/10.3390/ijms140612780

7. Liu, T., Zhang, L., Joo, D., & Sun, S. C. (2017). NF-κB signaling in inflammation. Signal transduction and targeted therapy, 2, 17023–. https://doi.org/10.1038/sigtrans.2017.23

8. Smith, A. G., Miles, V. N., Holmes, D. T., Chen, X., & Lei, W. (2021). Clinical Trials, Potential Mechanisms, and Adverse Effects of Arnica as an Adjunct Medication for Pain Management. Medicines (Basel, Switzerland), 8(10), 58. https://doi.org/10.3390/medicines8100058

9. Gaertner, K., Baumgartner, S., & Walach, H. (2021). Is Homeopathic Arnica Effective for Postoperative Recovery? A Meta-analysis of Placebo-Controlled and Active Comparator Trials. Frontiers in surgery, 8, 680930. https://doi.org/10.3389/fsurg.2021.680930

10. Ernst E, Pittler MH. Efficacy of Homeopathic Arnica: A Systematic Review of Placebo-Controlled Clinical Trials. Arch Surg. 1998;133(11):1187–1190. doi:10.1001/archsurg.133.11.1187

11. Avogadro’s number is a constant used in chemistry and physics. It indicates how many molecules or atoms are contained within a mole of a specific compound. The number is usually calculated as a value of 6.022*10^23.

12. Not the level of supposed bruising and harm that Amber has been suggested of sustaining from Depp.