Palo santo is recommended for a wide range of health issues including immune boosting, muscle and joint aches, allergies, headaches and as a bug repellant. And the list goes on (that is if you indiscriminately believe what you read on the internet).
I hate to be difficult but palo santo is a tree so which part of the tree exactly are we talking about here – the roots, the bark, the leaves, the fruit or maybe an oil extract?
Table of Contents
- 1 What Is Palo Santo?
- 2 Is There Any Research?
- 3 Conclusion
What Is Palo Santo?
Palo santo (Bursea graveolans), also known as ‘holy wood’ is native to Mexico, Peru and Venezuela. Different parts of the tree are used by different medical systems (shamanism, indigenous medicine and complimentary medicine).
The bark of the tree is used in shamanic traditions. The bark is burned and the sweet scented smoke is believed to cleanse energies and carry intentions to the universal spirit. Smudging with palo santo is also used to cleanse the energy of people and places in more modern space clearing and feng shui ceremonies.
The leaves of the tree are used topically to treat mosquito bites, stomach pains, skin infections and arthritis in local indigeous medical practice (1).
The oil is used in complimentary medicine and also in the beauty industry.
It is the fruit of palo santo tree that is used for essential oil extraction. The essential oil yield from the fruits is high (3%) (2). This still leaves a significant waste biomass of 97% which is the subject of much interest in the research community as to how best to deal with this biomass (2).
A Utah based essential oil company analyzed the composition of palo santo oil by mass spectrometry chromatography and identified the key components as limonene (58.6%) and alpha-terpineol (10.9%) (3). Another study done in Cuba also found limonene to be the key component in palo santo oil albeit at a lower percentage (26.5%) (4).
The tree is protected in many countries and only wood that has fallen can be taken for use.
Is There Any Research?
There are a total of 6 published studies on palo santo in the medical literature. To put this into context, research into cinnamon (a valid comparison as a tree source of another popular essential oil) stands at almost 2000 published papers.
Not a single one of the 6 published papers on palo santo is a clinical trial. In fact, none of these studies have anything to do with humans. In the absence of human data, it would be resonable to look for animal data. Only two of the 6 studies have anything to do with animals. However one paper is on the importance of animals in the spread of palo santo seeds (5). Hardy relevant. So now we are down to one animal study and four non-human non-animal studies.
Does It Enhance The Immune System?
There are no studies to support a role for palo santo as an immuno-enhancer. In the absence of research data or animal data, we are left with assessing the biological plausability of this claim. This is a very crude method of approximation and a very poor substitute for real research. But here goes.
None of the key components of palo santo oil would be classically associated with immunomodulation. There are a handful of animal studies on limoene but the results are conflicting and hard to interpret. So even at a stretch there is nothing that we could reliably draw on to support the role of palo santo an an immunomodulator.
Summary: There is neither clinical evidence nor convincing biological plausability behind claims that palo santo enhances the immune system.
Does It Detoxify?
This is a little complex. By western allopathic medical science standards, there is no science to support the fact that palo santo can detoxify. So where do the claims come from. Other popular blogs claim that plao santo can detoxify but provide no references (I think we know why that would be).
Palo santo is used in smudging in shamanic traditions. I wonder if the claims about detoxification have been extrapolated from shamanic medicine.
Summary: There is no science to support a role for palo santo in detoxification.
Is It A Relaxant?
There are no studies to suggest a role for palo santo as a relaxant. Again in the absence of data, let’s look at biological plausability. Palo santo is an aromatic oil and aromatic oils are believed to impact positively on the stress repsonse. It is biologically plausible (though unproven) that palo sano could help with relaxation.
Summary: There are no studies to support cliams that palo santo acts as a relaxant.
Does It Treat Headaches?
There are no studies or case reports (or anything) connecting palo santo with the relief of headaches.
Summary: Claims that palo santo treats headaches are misleading.
Does It Treat Colds or Flu?
Yet again, the scientific literature comes up with ‘no match found’ for the search terms ‘palo santo’ and ‘cold or flu’. Equally there is nothing if we extend the search to viral infections in general.
Summary: There is no evidence behind claims that palo santo treats cold, flu or viral infections.
Does It Reduce Joint or Muscle Pain?
A number of publications and blogs mention the use of palo santo in the treatment of rheumatism. Some of these papers and blogs reference a 2005 Japanese study as the citation for the claim (6). Finally, a reference we can evaluate and it is also one one our 5 papers. The paper written by Nakanishi is a cell biology paper entitled Cytotoxic Aryltetralin-Type Lignans from Stems of Bursera graveolens.
The paper has nothing at all to do with rheumatism but does mention in the introduction that palo santo was used in traditional medicine for rheumatism. Nakanishi quote a 1981 book on medicinal plants as the reference for the claim on rheumatism (7). What this means is that palo santo has been used in indigenous medicine for the treatment of rheumatism.
That’s it and that’s all.
Using a cell biology paper as a reference is misleading as it could imply that there is cell biology data linking palo santo and rheumatism. This is not the case.
Summary: The use of palo santo for rheumatism has no scientific basis.
Is It A Bug Repellant?
There are no clinical studies looking at the bug repellant properties of palo santo. It is biologically plausible that palo santo could have some bug repellant properties due to the high limonene content. Additionally palo santo has been used in indigenous medicine to treat mosquito bites.
The only study of relevance (vaguely) is some in vitro data to suggest that palo santo may inhibit the growth of the neglected tropical trypanosome infection cause by Leishmania amazonensis (8).
Summary: There is no scientific proof to support the use of palo santo as a bug repellant but it is biologically plausible.
Is It An Allergy Reducer?
There is nothing in the scientific medical literature nor in indigenous medicine to suggest a role for palo santo to reduce allergies.
Summary: There is no evidence to support the use of palo santo for allergies.
Is Palo Santo Safe?
There is one report in the literature of intoxication of animals which was attributed to ingestion of seeds of the palo santo tree (9). That is the second animal study out of total of six publications on palo santo.
Terpineol is irritant to mucous membranes including the eyes. It can also cause hemorrhagic gastritis, central nervous system depression, hypothermia and respiratory depression.
Limonene is also irritant to the eyes and mucous membrane and is associated with liver cell damage.
Essentially palo santo is used in three very different medical systems (shamanism, indigenous medicine and complimentary medicine). The use of palo santo in shamanism is separate and outside the scope of this article.
There is no science to recommend the use of palo santo in either indigenous or complimentary medicine.
Let me leave you – in particular you who is a little more skeptical of the science – a final fun fact.
A key opinion leader on palo santo carried out a prescribing survey among health care professionals in Mexico (10). Almost 50% of 1614 health care workers interviewed said that they prescribed or recommended medicinal plants for patients. A total of 77 plant species, belonging to 40 botanical families, were used for medicinal purposes as reported by the survey participants.
Palo santo (Bursera graveolans) did not feature in the list.
It is curious that practitioners who were open to prescribing medicinal herbs and who had access to palo santo did not prescribe or recommend it to their patients.
With no scientific base and knowing that local practioners do not even prescribe palo santo, it is irresponsible to recommend the use of palo santo for any health reasons.