Some essential oils such as tea tree* have demonstrated anti-microbial effects, but there is still a lack of clinical evidence demonstrating efficacy against bacterial, fungal, or viral infections. Evidence for the efficacy of aromatherapy in treating medical conditions remains poor, with a particular lack of studies employing rigorous methodology,* but some evidence exists that essential oils may have therapeutic potential.*
HistoryMany such oils are described by Dioscorides, along with beliefs of the time regarding their healing properties, in his De Materia Medica, written in the first century.* Distilled essential oils have been employed as medicines since the invention of distillation in the eleventh century,* when Avicenna isolated essential oils using steam distillation.*The concept of aromatherapy was first mooted by a small number of European scientists and doctors, in about 1907. In 1937, the word first appeared in print in a French book on the subject: Aromathérapie: Les Huiles Essentielles, Hormones Végétales by :fr:René-Maurice Gattefossé|René-Maurice Gattefossé, a chemist. An English version was published in 1993.* In 1910, Gattefossé burned a hand very badly and later claimed he treated it effectively with lavender oil.*A French surgeon, :fr:Jean Valnet|Jean Valnet, pioneered the medicinal uses of essential oils, which he used as antiseptics in the treatment of wounded soldiers during World War II.*
Modes of applicationThe modes of application of aromatherapy include:
MaterialsSome of the materials employed include:
TheoryAromatherapy is the treatment or prevention of disease by use of essential oils. Other stated uses include pain and anxiety reduction, enhancement of energy and short-term memory, relaxation, hair loss prevention, and reduction of eczema-induced itching.*
Two basic mechanisms are offered to explain the purported effects. One is the influence of aroma on the brain, especially the limbic system through the olfactory system.* The other is the direct pharmacological effects of the essential oils.* While precise knowledge of the synergy between the body and aromatic oils is often claimed by aromatherapists, the efficacy of aromatherapy remains unproven. However, some preliminary clinical studies of aromatherapy in combination with other techniques show positive effects. Aromatherapy does not cure conditions, but helps the body to find a natural way to cure itself and improve immune response.*In the English-speaking world, practitioners tend to emphasize the use of oils in massage . Aromatherapy tends to be regarded as a complementary modality at best and a pseudoscience|pseudoscientific fraud at worst.*
Choice and purchaseOils with standardized content of components (marked FCC, for Food Chemical Codex) are required to contain a specified amount of certain aroma chemicals that normally occur in the oil. There is no law that the chemicals cannot be added in synthetic form to meet the criteria established by the FCC for that oil. For instance, lemongrass essential oil must contain 75% aldehyde to meet the FCC profile for that oil, but that aldehyde can come from a chemical refinery instead of from lemongrass. To say that FCC oils are "food grade" makes them seem natural when they are not necessarily so.
Undiluted essential oils suitable for aromatherapy are termed 'therapeutic grade', but there are no established and agreed standards for this category. The market for essential oils is dominated by the food, perfume, cosmetics and pharmaceutical industries, so aromatherapists have little choice but to buy the best of whatever oils are available.
Analysis using gas liquid chromatography (GLC) and mass spectrometry (MS) establishes the quality of essential oils. These techniques are able to measure the levels of components to a few parts per billion. This does not make it possible to determine whether each component is natural or whether a poor oil has been 'improved' by the addition of synthetic aromachemicals, but the latter is often signaled by the minor impurities present. For example, linalool made in plants will be accompanied by a small amount of hydro-linalool, whilst synthetic linalool has traces of dihydro-linalool.
EfficacyThere is little evidence to date about the efficacy of aromatherapy.
Martin et al. (1996) concluded that most of the clinical trials suffered from various confounding factors, such as a lack of adequate control, small sample sizes, and lack of repetition by independent researchers. As well, many are served in conjunction with other possible influencers. One example being Kuritama et al.'s (2005) experiment where the psychological benefits of aromatherapy massage was compared to massage alone. Once the tests and questionnaire measures were evaluated there showed a significant reduction in anxiety and self-ranked depression, though there was no difference between the two groups.
Aromatherapists tend to back up their belief in their practice by saying that one cannot confirm or reject their methods by using scientific approaches, because science is reductionist and that aromatherapy depends on a holistic method (Schnaubelt 1998).
Some benefits that have been linked to aromatherapy, such as relaxation and clarity of mind, may arise from the placebo effect rather than from any actual physiological effect. The consensus among most medical professionals is that while some aromas have demonstrated effects on mood and relaxation and may have related benefits for patients, there is currently insufficient evidence to support the claims made for aromatherapy.* Scientific research on the cause and effects of aromatherapy is limited, although in vitro testing has revealed some antibacterial and Antiviral drug|antiviral effects.* There is no evidence of any long-term results from an aromatherapy massage other than the pleasure achieved from a pleasant-smelling massage.* A few double blind studies in the field of clinical psychology relating to the treatment of severe dementia have been published.* Essential oils have a demonstrated efficacy in dental mouthwash products.*Mainstream literature suggests that aromatherapy is based on the anecdotal evidence of its benefits rather than proof that aromatherapy can cure diseases. Scientists and medical professionals acknowledge that aromatherapy has limited scientific support, but critics argue that the claims of most aromatherapy practitioners go beyond the data, and/or that the studies are neither adequately controlled nor peer reviewed.
Some proponents of aromatherapy believe that the claimed effect of each type of oil is not caused by the chemicals in the oil interacting with the senses, but because the oil contains a distillation of the "Vitalism|life force" of the plant from which it is derived that will "balance the energies" of the body and promote healing or well-being by "purging negative vibrations" from the body's "energy field". Arguing that there is no scientific method|scientific evidence that healing can be achieved or that the claimed "energies" even exist, many scientific skepticism|skeptics reject this form of aromatherapy as pseudoscience.
Safety concernsIn addition, there are potential Alternative medicine#Criticism|safety concerns. Because essential oils are highly concentrated they can irritate the skin when used in undiluted form.* Therefore, they are normally diluted with a carrier oil for topical application, such as jojoba oil, olive oil, or coconut oil. phototoxicity|Phototoxic reactions may occur with citrus peel oils such as lemon or Lime (fruit)|lime.* Also, many essential oils have chemical components that are Stimulus (physiology)|sensitisers (meaning that they will after a number of uses cause reactions on the skin, and more so in the rest of the body). Some of the chemical allergies could even be caused by pesticides, if the original plants are cultivated.* Some oils can be toxic to some domestic animals, with cats being particularly prone.*Two common oils, lavender and Melaleuca alternifolia|tea tree, have been implicated in causing gynaecomastia, an abnormal breast tissue growth, in prepubescent boys, although the report which cites this potential issue is based on observations of only three boys (and so is not a scientific study), and two of those boys were significantly above average in weight for their age, thus already prone to gynaecomastia.* A child hormone specialist at the University of Cambridge claimed "... these oils can mimic estrogens" and "people should be a little bit careful about using these products."* The study has been criticised on many different levels by many authorities. The Aromatherapy Trade Council of the UK has issued a rebuttal* The Australian Tea Tree Association, a group that promotes the interests of Australian tea tree oil producers, exporters and manufacturers issued a letter that questioned the study and called on the New England Journal of Medicine for a retraction (ATTIA).* The New England Journal of Medicine has so far not replied and has not retracted the study.
As with any bioactive substance, an essential oil that may be safe for the general public could still pose hazards for pregnant and lactating women.
While some advocate the ingestion of essential oils for therapeutic purposes, licensed aromatherapy professionals do not recommend self prescription due the highly toxic nature of some essential oils. Some very common oils like Eucalyptus are extremely toxic when taken internally. Doses as low as one teaspoon have been reported to cause clinically significant symptoms and severe poisoning can occur after ingestion of 4 to 5 ml.* A few reported cases of toxic reactions like liver damage and seizures have occurred after ingestion of sage, hyssop, thuja, and cedar.* Accidental ingestion may happen when oils are not kept out of reach of children.
Oils both ingested and applied to the skin can potentially have negative interaction with conventional medicine. For example, the topical use of methyl salicylate heavy oils like Sweet Birch and Wintergreen may cause hemorrhaging in users taking the anticoagulant Warfarin.
Adulterated oils may also pose problems depending on the type of substance used.