Historical & Current Uses
essential oil: Function: noun: any of a large class of volatile odoriferous oils of vegetable origin that impart to plants odor and often other characteristic properties, that are obtained from various parts of the plants (as flowers, leaves, or bark) by steam distillation, expression, or extraction, that are usually mixtures of compounds (as terpenoids, aldehydes, or esters), and that are used often in the form of essences in perfumes, flavoring materials, and pharmaceutical preparations — called also ethereal oil, volatile oil; distinguished from fatty oil and fixed oil. Webster’s Third New International Dictionary, Unabridged. Merriam-Webster, 2002.
herb: Function: noun: Inflected Form(s): -s Usage: often attributive Etymology: Middle English erbe, herbe, from Old French, from Latin herbe. 1 : a seed-producing annual, biennial, or herbaceous perennial that does not develop persistent woody tissue but dies down at the end of a growing season. 2 : a plant or plant part valued for its medicinal, savory, or aromatic qualities <under herbs I have included laurel leaves — J.W.Parry>. 3: archaic : GRASS, VEGETATION <underfoot the herb was dry — Alfred Tennyson>. 4 : the leafy top of an herbaceous plant considered separately from the root. Webster’s Third New International Dictionary, Unabridged. Merriam-Webster, 2002.
What are Essential Plant Oils?
Many years ago, while digging into the vagaries of herbal science, I pondered the meaning behind the expression “essential plant oil.” My first guess? That these words reflected the importance of such oils to the plants they came from. It was a natural conclusion. Their ability to protect plants from insects, fungi, bacteria, and viruses was–and is–well known. None can doubt they are essential to the plants’ survival.
Yet, etymologically speaking, I was mistaken. Essential plant oil, as a descriptor used in herbal science, says almost nothing about the relation between such oils and the plants that produce them. Instead, it speaks to how those oils imbue essential qualities upon the perfumes, flavorings, attractants, repellents, pesticides, poisons, and pharmaceuticals formulated from them.
This focus, on exploitation, is an artifact of a lengthy and profitable–though somewhat esoteric–past. The household, medicinal, and prescriptive uses of essential oils are described in some of the most ancient records known. The history of herbal science, as reconstructed from a huge body of public and private records, chronicles man’s development and application of the arts of medicine, healing, disease prevention, and pest management. Some of what ancient herbalists learned entered the public domain as soon as the discoveries took place, but much was also kept secret–often for centuries–to curry favor with the elites and the ruling classes. Much could be achieved by conferring special advantages upon such people, while concealing the same from the common man. In any case, essential oils continue to be used, today, in each of these arts, and for a myriad of diverse applications. Rarely, concentrated essential oils are used. Diluted oils, powders and coarsely or finely chopped preparations of fresh or dried flowers, leaves, stems, and roots, supply the herb’s valuable properties to the user, either directly–in pills, capsules, teas, infusions, and decoctions–or indirectly–in salves and dilute carrier oils.
In light of all this, it seems paradoxical that herbal science is not championed–or even respected–everywhere, or by everyone. Unenlightened “experts” often equate the use of essential oils to quackery, old wives tales, and the brews of witches. In fact, some of our most authoritative professional associations, particularly in the fields of medicine and pest management, have lent support to that equation despite a mountain of easily verified facts that tells quite another story. In medicine alone, over 25 percent of today’s most valuable prescription and over-the-counter drugs contain, as key ingredients, herbal extracts. Many of today’s most successful pesticides are also based on herbal extracts. A much larger fraction of important products in both groups includes synthetic versions of chemicals that originally came only from herbal sources.
Provocative examples abound. One is the active ingredient used in modern aspirin. That ingredient is a modified salicylate, the acetyl derivation of salicylic acid. Raw salicylates were first used as medicines over 5,000 years ago, as herbal preparations from the willow plant. We know this because a stone tablet devoted to medicine, dating from the Third Dynasty of Ur (ca. 3000 BCE), contains cryptic descriptions of remedies based on willows. Over the ensuing centuries, the efficacy of such extracts became well known and widespread. The Ebers Papyrus (ca. 1543 BCE), an Egyptian medical text, details how willow and myrtle plants were used for analgesic, anti-inflammatory purposes. Today, among all the medicines known, aspirin is one of the most widely prized. But it is not unique in having its origins in herbal science. Thousands of other important and widely used medicines have near-identical roots. It is no exaggeration to assert that, were all herb-derived medications withdrawn from our pharmacies and drug stores, medical science would revert to a state remarkably like that of the Dark Ages.
Pest management has also been blessed by discoveries of herbal preparations that exterminate and repel vermin and pests. Some–for example, red squill, extracted from bulbs of the sea onion lily (Urginea maritima), and cited in ancient stone tablets for its utility as a rat poison–are as poisonous to humans as they are to rats. Others–for example, pyrethrum extracts of chrysanthemum flowers–kill insects on contact, but produce only transitory effects on humans. Still others–and this is the group that excites me the most–are exceptional pesticides and pest repellents yet, wonder of wonders, are entirely harmless to humans, dogs, and cats; some in this latter group are based on essential oils that we regularly use in our kitchens as health-enhancing dietary ingredients and culinary flavorings.
Far from quackery, then, herbal science is the keystone of the foundation on which the arts of modern medicine, disease prevention, and pest management are built. Yet, notice this: less than 2 percent of the herbs known to exist on earth have undergone serious analysis of their herbal characters. Do you realize what this means? Important, earth shaking discoveries await our careful investigation, analysis, and testing. It is a safe bet that the future of herbal science is secure, and will be every bit as glorious as its past.
Glorious, indeed. But what about our present knowledge? What–contrariwise–of the abundant misinformation about herbal science that leads so many to unfairly distrust it? I added the qualifier “unfairly” for a reason. Thinking persons should never trust anything without good cause, so we shouldn’t give herbal science carte blanche control over any aspect of our lives, but neither should we reject that science out of hand. Aspirin is only one of its many known gifts. How many more gifts from that source are capable of improving, extending, or even saving, your life and the lives of those you love? Expect to be pleasantly surprised by the answers to that question, but also expect to have to dig a little to come face to face with those answers, as most are neither common knowledge nor broadcast in loud, visible ways. Some, in fact, are so well hidden that serious sleuthing is required to bring them to light.
Recovering at least part of the veiled, lost, even undiscovered knowledge on this subject is one purpose of the material presented here. Encouraging others–like you and your family–to delve deeper and conduct your own investigations, is another. Methinks you owe that to yourself, and to your posterity, especially now that you can get involved more easily than in the past. We are fortunate that, in these early years of the new millennium, a renewed interest in, and appreciation for, herbal science can be seen all around us.
In this article, I touch only lightly on the (internal) medicinal properties of essential plant oils. My primary focus is on external applications, including the use of essential plant oils as bacterial and viral microbicides, broad-band insecticides, fungicides, and acaricides, and as repellents of spiders, scorpions, flies, mosquitoes, frogs, lizards, and snakes. In the process, it is shown that although we still have much to learn, a rich body of ancient but valuable knowledge already exists. One can only guess at the huge store of undiscovered truths that await our discovery, but it would be folly to presume that store to be anything less than a significant multiple of what we already know.
Essential Plant Oils in Antiquity
We needn’t dig very deep to find ample evidence that essential plant oils have been used by mankind for as long as humans have gathered together in communal settings. It seems logical that the humans who used them sought to satisfy many, if not most, of the same needs addressed in a similar fashion today. Now, as presumably then, the objectives served are quite simple, focusing as they do on relieving human misery, improving human health, and extending human life.
When archeologists excavate Neolithic sites dating from 4,000-7,000 BCE, they sometimes find scattered evidence suggesting that the occupants of those sites were combining certain plants, known to contain high fractions of volatile essential oils, with olive and sesame oils to produce what we would today describe as ointments. In 1975, Dr. Paolo Rovesti found a terra-cotta implement, in a Taxila museum in the Indus Valley, that appeared as a crude still; it was displayed along with terra-cotta perfume containers that dated around 3,000 BCE. Later, a similar implement, in this case clearly a still that dated to 2,000 BCE, was uncovered in Afghanistan. Such stills likely were used to extract essential oils from local aromatic botanicals.
Tablets from Babylonia, written in cuneiform, have been found that contain orders–to import cedar, myrrh, and cypress–among recipes for scented ointments and descriptions of medicinal uses for cypress. In Asia, similar writings dating to 2697 BCE, describe how aromatic herbs should be used. Biblical passages describe recipes for holy anointing oils for priests that include–in an olive oil base–the fragrant ingredients myrrh, cinnamon, and calamus. Other references to essential oils, from the Old and New Testaments, number in the hundreds, and testify to their ancient uses in practically every venue that such oils are utilized in today.
The Americas, Europe, and Asia
In the Americas, archeological digs show that the most ancient of natives studied and used herbal science from the earliest of times. European settlers, within decades of the discovery of the New World, subjected the native herbs they found to intense study, seeking to learn the properties of their essential oils. Native Americans, already steeped in the lore of these herbs, freely–even eagerly–shared their knowledge and understanding. For example, the Ojibwa Indians who lived near the Great Lakes explained to the settlers why they took such great pains to gather a hardy swamp perennial that eventually came to be known as Joe Pye weed (often cited as Eupatorium purpureum, but probably any or several of a number of species in the genus Eupatorium that have whorled leaves), and how they used it for a multitude of medicinal purposes, including the prevention and treatment of kidney stones.
Having some Native American blood in my veins, I have a special interest in the ways Native Americans studied and used botanical extracts. Their unselfish–often naive–willingness to pass this lore on to others, withholding nothing and expecting little or no recompense for sharing nature’s truths, is a model worthy of, at the very least, an enlightened form of emulation. It is undeniable that the European settlers in the New World benefited greatly from the body of knowledge bequeathed by their native hosts, but the sharing didn’t stop there. For example, a 19th-century Native American herbalist and healer known as Joe Pye (possibly a transliteration of a native American name, e.g., Zhopai) was reputed to have saved an entire colony of European settlers from the scourge of epidemic typhus by serving them decoctions of Eupatorium herb. The medicine is reported to have caused them to sweat profusely, thus cleansing their bodies of typhus toxins.
Besides such examples from North America, Eupatorium extracts have a long history of usage elsewhere, including Asia, but also in Western Europe. In the Mediterranean basin, its use dates to a time prior to the reign of Mithridates VI Eupator of Pontus (c. 119-63 BCE), after whom the genus is named. Mithridates is thought to have used the herb as a remedy or an antidote, though the exact applications have been lost. It seems likely that the medics of the day discovered many if not most of the herb’s rather easily demonstrated properties, and took advantage of them accordingly. However, unlike the simplistic mores of many Native American Indians, it was characteristic of some, if not most, Old World cultures to reserve the body of esoteric knowledge surrounding herbs and their extracts for society’s most powerful members. Which helps explain why ancient public records on herbal science are often terse and cryptic.
A Famous, Ironic Use of an Essential Plant Oil
Not all ancient uses of essential plant oils were shrouded in secrecy, and not all such applications benefited the recipient.
Socrates, a veteran of the Athenian military, as a young man participated in the Peloponnesian war. In his later years he became the quintessential questioner of all things taken for granted. His peripatetic style of discourse and teaching of mores, ethics, and governance–by forcing his students to examine life and all its aspects with fresh eyes and open minds–ranks him among the greatest philosophers in all of history. His reward was to be sentenced to death after being convicted of, among other things, impiety. His fate was sealed by a democratic jury of dikasts who worried that democracy risked too much when its citizens were goaded into thinking too freely.
Socrates was executed in 399 BCE. He and his supporters, resigned to his fate, chose to have the court’s sentence carried out by having him drink a decoction of hemlock (Conium maculatum).
Progressively, the piperidine alkaloids in the essential oils of the hemlock plant paralyzed Socrates’ body, reaching in due course the muscles of respiration. As expected, this caused the philosopher to suffer a fatal respiratory arrest. Hemlock was chosen because its toxic properties, and the relatively painless way it works, had already been known and publicized for centuries.
A Reprehensible, yet Efficacious Application of Essential Plant Oils
One of the most reprehensive utilizations of essential oils took place during one of the middle bubonic plagues. A series of these scourges devastated Central Asia, the Middle East, Europe and the British Isles. The sequence began in the 6th century CE, when the first recorded plague ravaged the Byzantine Empire, and ended in 1665-1666, when the last outbreak took place in Europe.
In the narrative that follows, I am purposely vague about dates and locations. Many versions of this story are in print, and some are attributed to unusually credible sources. However, important variations in the details exist. This justifies a certain skepticism, not as much about the core features of the story, as about the minute details themselves. Accordingly, I am conducting additional research, in hopes of getting closer to the truth of those details, and will make appropriate revisions as those emerging truths dictate:
A cloud of superstition enveloped the bubonic plague during the years of its worst manifestations. Its cause is now known to be the bacterium Yersinia pestis, which is spread by fleas infesting the rats and mice that carry the bacterium. Many years passed, however, before the role of the rat flea (Xenopsylla cheopis) came to light. In the meantime, various theories–steeped in and shaped by the religious and mystical lore of the day–were bandied about to explain why the disease had visited man, and how it spread within the population.
Most theories assumed that vapors of one kind or another were involved, since coming into close association with an infected person, even for a short time, was enough to contract the disease. Since everybody knew how risky it was to chance an exposure, the homes of plague victims were usually abandoned, unguarded, to the dead and dying. Still, a few enterprising criminals–enticed by the quantity of costly goods, jewels, and precious coins ripe for the taking in such places–took to looting not only the victim’s homes, but the sickened bodies and corpses of the human victims as well. Many of these miscreants contracted the plague in the process, but one group of four did not, despite–we are told–having carried on a long, lucrative career of such thievery. That career eventually came to an end, when the group was caught, convicted, and sentenced to death by burning at the stake.
Before the death sentence was executed, a representative of the reigning monarch interrogated the condemned. The most pressing question asked was how they had managed to come into direct contact with so many plague victims without contracting the disease. Did they, as others had intimated, make use of hitherto secret, protective concoctions?
The prisoners confessed that secret concoctions were, indeed, involved. However, they balked at divulging the nature of those concoctions unless their sentences were reduced. When the king agreed, the prisoners revealed that, prior to engaging in their spree of looting, they had worked in one capacity or another for the perfume trade. Over time they had become privy to carefully guarded secrets regarding the unpublished characters of certain essential oils, including the fact that those oils, when applied to one’s skin, hair, and clothing, would protect the bearer from contracting certain diseases such as the bubonic plague. After stealing quantities of these essential oils, they mixed up a batch for their own use, but instead of using it for good, they chose to apply it as a means of facilitating their criminal behavior.
This confession was dutifully written down and filed away in the king’s annals. However, neither the precise formula they used, nor the list of essential plant oils involved, was included with the official record of the confession. Some speculate that the king and his courtesans considered such details to be so valuable that–rather than publish them abroad as a means of saving lives–they kept them secret, thus (to my way of thinking) perpetuating the sins of the thieves.
Many years later, the confession was rediscovered and a host of analysts–chief among them the French physician and herbalist Jean Valnet–took great pains to delve into the panoply of available essential oils, hoping to divine which among them might have performed as the convicted looters described.
Knowing, by now, the role played by the rat flea in transmitting Yersinia pestis from rats to humans, these analysts knew what the essential oils would have to do. Each would need to (1) efficiently kill or neutralize bacteria, including Yersinia pestis, on contact, (2) quickly kill or neutralize rat fleas before they could bite, and/or (3) successfully repel rat fleas so well that they would not be given an opportunity to bite. Because the essential oil trade in existence at the time the prisoners confessed included fewer spices than are commonly traded today, the list of candidates was relatively short and easily resurrected.
The candidates on that list, as described below, were subjected to careful examination to see what roles, if any, they might have played in protecting ordinary individuals from the bubonic plague. Over time, the investigators were gratified to discover that many of these essential oils satisfied one or more of the stated criteria. Surprisingly, several of them satisfied all three.
Powerful Antibacterials, Antiviruses, Pesticides, and Pest Repellents
Four important spices of antiquity–cloves (Syzygium aromaticum, syn. Eugenia aromaticum), cinnamon (Cinnamomum verum), nutmeg (Myristica fragrans), and bay laurel leaf (Laurus nobilis)–contain high fractions of a phenylpropanoid known as eugenol. Even when cut to less than one percent of the potency found in undiluted essential clove bud oil, eugenol kills rat fleas on contact and repels rat fleas by its vapors alone. Eugenol also has analgesic, antiseptic, microbicidal, antihelminthic, and anesthetic properties.
Cypress (Cupressus sempervirens) oil contains the monoterpenes camphene, cymene, and pirene. These natural insecticides and insect repellents also have antiseptic, microbicidal, and fungicidal properties.
Cedarwood (Juniperus spp.) oil contains cedrol, cedrene, and the terpene thujopsene, which kill and repel insects besides having antiseptic, bactericidal, and fungicidal properties.
Citrus (Citrus spp.) oil, whether from orange, lemon, or lime, contain high fractions of the cyclic terpene limonene, and the terpene alcohol linalool, both of which kill and repel insects, serve as microbicides and fungicides, and act as solvents. It is likely that, as with penicillin’s ability to strip the protective outer coating from dangerous microbes, their ability to dissolve the protective coatings and skins of noxious fungi, insects, and arachnids plays a prominent role in their pesticticidal faculties.
Rosemary (Rosemarinus officinalis) oil contains the phenolic diterpenes carnosic acid and rosmarinic acid, which are broad-band insecticides, insect repellents, and microbicides.
Elecampane (Inula helenium) root oil, harvested from plants no more than two or three years old, contains the stearoptene helenin, a powerful antiseptic and bactericide that has recently been shown capable of destroying the modern-day “superbug” methicillin-resistant Staphylococcus aureus, or MRSA, besides a broad spectrum of other bacteria including Yersinia pestis.
Angelica (Angelica sylvestris) root contains β-terebangelene, which is effective against various bacteria, including Yersinia pestis, as well as against fungal infections and viruses.
Wormwood (Artemisia absinthium) oil contains the bitter elements absinthine and anabsinthine, and among others, the ketone and monoterpene thujone; both absinthine and anabsinthine are powerful vermicides, insecticides, and bactericides.
Sage (Salvia officinalis) oil contains cineole, borneol, and thujone; both cineole and borneol are powerful insect repellents, though pure cineole–which is also found to some extent in essential oils of bay leaves, wormwood, rosemary, and others–while repelling most insects, including rat fleas, is an attractant of orchard bees, which probably gather it to synthesize pheromones.
More To Come…
——–
Did this brief article help you understand the value of essential oils as natural medicines, pesticides, and pest repellents? I hope it did. Ignorance about the existence, and efficacy, of natural essential oils that function in such roles, is not unusual today. Rather than discouraging you, that fact should make you want more than ever to get involved in helping us fill in the gaps and make strides forward in our understanding and knowledge. The field is still wide open, quite contrary to what you may have previously believed. Step forward and do something positive that cranks our knowledge upward. If you have questions about essential oils and how they might benefit you and your family, feel free to leave a comment below. Comments on postings here are moderated quickly, and replied to personally using the commenter’s email address. Whenever possible, every inquiry is answered immediately–in fact, I try to answer within minutes of reading each comment.