Sandalwood Essential Oil
Sandalwood - General Info
Sandalwood is the wood of trees from the Santalum genus. Called the world's most valuable tree, it is aromatic and prized for its essential oil - which has been used since ancient times in the making of incense, perfumes and other scented products. 
Sandalwood's unique, rich fragrance is always in demand and this has led to over-harvesting of native Santalum album, Indian sandalwood. Sandalwood also finds itself on the list of fragrances considered aphrodisiac and with its rich, woody base note aroma, is commonly included in fragrance products designed for men. 
Santalum album is native to tropical India, the Indonesian Lesser Sundra Islands, and parts of northern Australia. Other species were native to other countries such as Hawaii and the Juan Fernández Islands (Chile) - however, sadly, some of these locations also have been overexploited to the point of possible extinction. 
Santalum / sandal trees are unusual in that they are semi-parasitic - meaning that their roots seek out the roots of other trees, which they tap for nutrients and water. For this reason they fare much better when grown alongside other species, which act as "hosts".  Santalum seeds appear to be somewhat temperamental; they cannot be stored and must be planted at the time of harvesting. It also takes years for the slow-growing trees to mature and produce a valuable sandalwood crop. For this reason, growing the trees commercially for sandalwood is not without challenges. 
Sandalwood Essential Oil
Sandalwood essential oil is traditionally produced from the heartwood and roots of the trees by a multi-stage distillation process.  The wood is ground to powder and then steam distilled. In modern times however, supercritical Carbon Dioxide is sometimes used to extract the sandalwood oil without using heat. As the heat of steam distillation alters some of the molecules, CO2 extraction results in a sandalwood oil that has a different scent profile to that which was steam distilled - and this is closer to the smell of the original wood (although this does not necessarily mean it is preferred as a fragrance). 
It is widely agreed that the older the sandalwood tree, the better the oil quality and the higher the oil content.  The trees take 60 to 80 years to reach full maturity  although they are often harvested much younger for quick profits.
History of Sandalwood
Sandalwood has been in use for at least 4,000 years in incense making, carving and fragrance production.  Since ancient times it has been associated with religious or spiritual ceremony, purification, divine inspiration and funerary rites.
The genus Santalum was first proposed by Linnaeus and he described Santalum album in 1753. 
The European Magazine of 1800 amusingly writes (of India) "The men are very effeminate, being exceedingly fond of ornaments, and anointing their bodies with sandalwood oil."
Sandalwood has certainly been grown commercially in Western Australia since prior to 1899 - when it was mentioned in the Queensland Agricultural Journal. 
Sandalwood was used in the traditional medicine of the Hawaiians including, interestingly, being powdered and made into a drink used for treatment of "diseases of both male and female sex organs" . Sandalwood found its way into 19th century preparations for gonorrhoea and these are described in Albert Ethelbert Ebert's Standard Formulary of 1897.  This practise appears to have traditional use - and a similar prescription for gonorrhea is described in William Dymock, J. H. Warden and David Hooper's 1893 Pharmacographia Indica as being practised in the traditional medicine of Southern India. 
Sandalwood Essential Oil Scientific Studies and Uses
Moving on to science - Sandalwood has been the subject of a fair amount of study, investigating its medicinal and chemical properties.
Sanalwood as aphrodisiac: It's claimed that the fragrance and chemical effects of sandalwood are similar to the effects of androsterone - considered by some to be a human pheromone. It's considered that sandalwood is more attractive to women hence its inclusion in fragrances designed for men.  Androsterone is found in male perspiration. 
Sandalwood is one of the few plant-based substances that has the peculiar honour of being described, in different times and places, as being wither aphrodisiac or anti-aphrodisiac. Whether by coincidence or not, such substances are often those associated with purification or religious ceremony - such as verbena. William Dymock's 1885 The Vegetable Materia Medica of Western India states that the "author of the Makhzan" considered sandalwood anti-aphrodisiac.  Presumably this work is the Makhzan al-adviyah ("The Storehouse of Medicaments") of 'Alavi Khan (d.1749 A.D.) / Hakim Muhammad Hadikhan 
I can find no literary source (Google books advanced search) prior to 1900 that mentions specifically that sandalwood is aphrodisiac. However in 1903: Cecil Boden Kloss's In the Andamans and Nicobars states: "Sandalwood and jessamine [i.e. jasmine] oil are held in great repute as aphrodisiacs, and are purchased from the Burmese traders in small quantities at a very high price.
Only one of the studies that I found, directly investigated the hormonal effects of the scent: A 2009 study at the Ecole Polytechnique Fédérale de Lausanne, Switzerland, found that synthetically-created sandalwood compounds were among molecules that specifically activated both olfactory receptors and the human nuclear estrogen receptor alpha. This study "may provide a direct functional link between the olfactory and hormonal systems in humans" - a result which could have profound significance for the fragrance industry, and for the scientific validation of scent aphrodisiacs. 
As with other essential oils that have been used in perfumery for centuries, it is quite likely that there is some chemical action that increases desire. It's known that the sense of smell is connected to sexuality and desire, and so it's not too much of a stretch to consider that plant molecules which are similar in certain functional ways to human pheromones, may have an aphrodisiac action. But more research is required. In a sense, the continued use in perfume attests to the fragrance's alluring quality. It seems that science is headed in the right direction and that within a few years, the medical world may have a deeper understanding of the complex relationship between scent and desire.
Santalum album (Sandalwood)
Sandalwood in aromatherapy: Sandalwood essential oil has been shown to affect different physiological parameters in humans upon inhalation. A 2006 placebo-controlled study at the Faculty of Life Sciences, University of Vienna, Austria found that Sandalwood oil elevated pulse rate, self-rated mood, attentiveness and other factors. These effects were found to be affected by perceived odor quality. α-Santalol, its primary constituent, also appears to positively influence attentiveness and mood. 
Currently, sandalwood essential oil is used in aromatherapy as an agent to relieve anxiety, stress, and depression because of its purported effects on the central nervous system. 
Sandalwood as anti-herpes agent: Schnitzler, Koch, and Reichling (2007) had demonstrated the susceptibility of both acyclovir-sensitive herpes simplex virus type 1 (HSV-1) strain KOS and acyclovir-resistant HSV-1 clinical isolates to sandalwood essential oil, which displayed high levels of virucidal activity against the said viruses in the study. Sandalwood essential oil had also significantly reduced the formation of plaque, and thus, sandalwood essential oil – along with other essential oils studied such as those from ginger, thyme, and hyssop – affected the virus before adsorption. Interfering or disrupting the virion envelope, which is involved in the process of adsorption to or entry into the host cells, may perhaps be the mechanism of action of the essential oils, including sandalwood essential oil, against HSV-1. The disruption in the viral envelope impairs the ability of HSV-1 to infect host cells.  An earlier Argentine study supports these findings, pointing out that sandalwood essential oil dose-dependently suppresses the replication of herpes simplex virus types 1 and 2 but such inhibitory effect being slightly decreased at higher multiplicity of infections. 
Sandalwood as antiseptic: Sandalwood essential oil has been used as an antimicrobial since old times. It is still used as an acne treatment for this reason but due to its strength it should be properly diulted with a carrier oil for this purpose. 
Sandalwood as anti-malarial: Sandalwood essential oil possesses antiplasmodial properties and appears to be active in vitro against Plasmodium falciparum (IC50 value of ≤1.0 g/mL) when administered subcutaneously in a rodent model. P. falciparum is well noted to cause the most dangerous form of malaria in humans, having rendered the highest rates of complications and mortality. 
Sandalwood as anti-cancer agent: Sandalwood is described as an old Ayurvedic remedy for inflammatory and eruptive skin diseases. Dwivedi and Abu-Ghazaleh (1997-2003) evaluated the chemopreventive potential of sandalwood essential oil against skin cancer, in a series of studies. In 1997 the team furnished evidence that sandalwood essential oil significantly lowered the papilloma incidence by 67%, multiplicity by 96%, and TPA-induced ornithine decarboxylase (ODC) activity by 70%. This chemopreventive property of sandalwood essential oil may be attributed to α-santalol, the chief component of sandalwood essential oil. The 1999 study also found that sandalwood oil prevented skin tumour development in mice. In the 2003 study of Dwivedi et al., wherein the chemopreventive effects of α-santalol were determined during the initiation and promotion phases in female CD-1 and SENCAR mice, the treatment of α-santalol somehow put off the development of papilloma during the promotion phase by 2 weeks in both CD-1 and SENCAR mice, significantly decreasing the papilloma incidence and multiplicity (p < 0.05) and significantly suppressing the ODC activity induced by TPA as well as the incorporation of 3H-thymidine in the DNA of mouse epidermis. 
Much of the additional scientific study on sandalwood focuses on the development of synthetic sandalwood compounds - no doubt destined for the perfume / fragrance product industry.
Sandalwood Essential Oil - Molecular Components and Chemistry
Sandalwood essential oil is mainly composed of sesquiterpene alcohols (e.g., santalol, bergamotol, and santalene).  The gas chromatography–mass spectrometry analysis results of Roh, Lim, Kim, and Park (2011) had listed the constituents of sandalwood essential oil to be as follows: α-santalol (45.8%), β-santalol (20.6%), β-sinensal (9.4%), and epi-β-santalol (3.3%). 
Sandalwood and the Environment
Due to their high commercial value, native sandal trees have been overharvested in many locations over the years, leading to serious depletion and some conservation efforts. However, there have been some serious challenges to conservation efforts - including ongoing illegal plunder of the trees (sometimes when too young), subsequent black market activity due to close monitoring of exports, and even violence.  For these reasons, some people are against the Sandalwood trade. The original forests of Mysore, India, traditionally associated with producing the best sandalwood, are said by some to be virtually depleted of mature trees  - although other (perhaps outdated) sources state that Mysore is the center of the world's supply. 
Sandalwood (Santalum album) is, perhaps thankfully, now being grown commercially on a large scale in Western Australia and Wikipedia states that Australia is now the world's largest producer of Santalum album; there are also plantations also in Vietnam, Vanuatu and New Caledonia (Pacific Islands) - although it is said by some that the best quality sandalwood oil comes from Mysore and Tamil Nadu - where the remaining trees are protected by law.
Sandalwood Oil Adulteration / Dilution
Not all of what is sold as sandalwood is actually the oil from Santalum album. Due to the extremely high commercial value of the genuine oil, it has often been adulterated.
Several other Santalum species have been sold as sandalwood, and while this may be "technically" and commercially acceptable (such as in the case of S. spicatum) the quality and "note" of the oils may vary from different Santalum species. Also, oils from other trees has been used as "sandalwood oil" - such as "false sandalwood" (Myoporum sandwicense), a native Hawaiian tree , and Amyris balsamifera  which, being less expensive, may find its way for example into sandalwood soaps. 
Nowadays however, Santalum album and other species are grown in plantations and this makes up most of the sandalwood sold. Also, other "carrier" or base oils are sometimes added, and it is not uncommon to see Sandalwood sold "in Jojoba" (Simmondsia chinensis) or even in coconut oil in order to make it go further. The Jojoba used may also have been refined in order to be more odorless and stable. 
In some cases, sandalwood oil may be adulterated with other synthetic aromas, or synthesized using chemical processes. It's said that the most expert practitioners are able to create adulterations that are very difficult to detect.  And for the buyer on the other side of the world, there is a good possibility that they will never know....
Some Santalum species
Santalum acuminatum (Desert Quandong)
S. album (Indian Sandalwood)
S. austrocaledonicum (Red / Yellow Sandalwood)
S. cignorum (West Australian sandalwood)
S. ellipticum (Coastal sandalwood)
S. freycinetianum (Freycinet sandalwood)
S. haleakalae (Haleakala sandalwood)
S. murrayanum (Bitter Quandong)
S. paniculatum (Hawai‘i sandalwood)
S. preissii (South Australian sandalwood)
S. salicifolium (Willowleaf Sandalwood)
S. spicatum (Australian sandalwood)
Sandalwood is listed in the AHPA's "Herbs of Commerce", p.270. 
Sandalwood - Other Names:
Sandalwood is also known as Santalum album (Latin), Iliahi (Hawai'i), Taggar (old name in India)
The information on this website is not medical advice, is not a substitute for medical consultation, has not been evaluated by the FDA and is not intended to diagnose, treat, cure any disease. Please seek advice from a medical professional if you have symptoms, are concerned about your health, or before using supplements or aphrodisiac products. Consult a qualified aromatherapist regarding the safe use of essential oils. Don't put essential oils undiluted on the skin, and never take them internally.
 Heuberger E., Hongratanaworakit T., & Buchbauer G. (2006). East Indian Sandalwood and alpha-santalol odor increase physiological and self-rated arousal in humans. Planta Medica, 72(9): 792–800. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/16783696
 Setzer W. N. (2009). Essential oils and anxiolytic aromatherapy. Natural Product Communications, 4(9): 1305–1316. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/19831048
 Schnitzler P., Koch C., & Reichling J. (2007).Susceptibility of drug-resistant clinical herpes simplex virus type 1 strains to essential oils of ginger, thyme, hyssop, and sandalwood. Antimicrobial Agents and Chemotherapy, 51(5): 1859–1862. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1855548/
 Benencia F. & Courrèges M. C. (1999). Antiviral activity of sandalwood oil against herpes simplex viruses-1 and -2. Phytomedicine, 6(2): 119–123. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/10374251
 Fujisaki R. et al. (2012).In vitro and in vivo anti-plasmodial activity of essential oils, including hinokitiol. Southeast Asian Journal of Tropical Medicine and Public Health, 43(2): 270–279. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/23082579
Plasmodium falciparum. Retrieved 22 March 2013 from http://en.wikipedia.org/wiki/Plasmodium_falciparum
 Dwivedi C. & Abu-Ghazaleh A. (1997). Chemopreventive effects of sandalwood oil on skin papillomas in mice. European Journal of Cancer Prevention, 6(4): 399–401. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/9370104
 Dwivedi C. et al. (2003). Chemopreventive effects of alpha-santalol on skin tumor development in CD-1 and SENCAR mice. Cancer Epidemiology, Biomarkers & Prevention, 12(2): 151–156. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pubmed/12582025
 Roh H. S., Lim E. G., Kim J., & Park C. G. (2011). Acaricidal and oviposition deterring effects of santalol identified in sandalwood oil against two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Journal of Pest Science (2004), 84(4): 495–501. Retrieved 22 March 2013 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3215870/
 "Herbs of Commerce" (AHPA) (2000 edition) - Michael McGuffin, John T. Kartesz, Albert Y Leung, Arthur O. Tucker p.270
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