Aromatic oils have been used for therapeutic purposes for nearly six thousand years (Buckle 2000). The ancient Chinese, Indians, Egyptians, Greeks, and Romans employed essential oils derived from plant materials in cosmetics, perfumes, and pharmaceuticals. Today, aromatherapy is gaining new attention as an alternative healing modality related to herbal medicine (Buckle 2000; Stevensen 1996).

Archeological evidence found in King Tutenkhamun's tomb and during excavations of the Indus Valley clearly demonstrates that essential oils were used during those times. The Old and New Testaments, written records from the ancient Greek physician Hippocrates, and European herbal texts also reveal that essential oils were employed commonly for spiritual, therapeutic, hygienic, and ritualistic purposes (Stevensen 1996).

René-Maurice Gattefossé, a French chemist, discovered the healing properties of lavender oil when he applied it to a burn on his hand after an explosion in his laboratory. Following this incidental finding, he devoted his time to analyzing the chemical properties of essential oils and to documenting their therapeutic value in treating burns, skin infections, gangrene, and wounds in soldiers during World War I (Stevensen 1996). In 1928, Gattefossé founded the science of aromatherapy (Buckle 2000; Buckle 1999; Stevensen 1996). In the 1950s, Marguerite Maury expanded the applications of aromatherapy in France to include uses by massage therapists, beauticians, nurses, physiotherapists, conventional doctors, and other healthcare professionals, an influence that continues to this day (Stevensen 1996). In France, more than 1,500 trained physicians employ essential oils as an alternative to antibiotics (Buckle 2000).

This alternative modality did not become widely known in the United States until the 1980s, when essential oils gained the attention of massage therapists, alternative practitioners, and the commercial industry. The lotions and beauty products currently sold under the guise of aromatherapy, however, usually contain synthetic fragrances, which lack the therapeutic components found in essential oils (Buckle 2000). While aromatherapy is one of the fastest growing complementary modalities, its commercial use and connection to the cosmetic industry has created some confusion about its therapeutic potential (Buckle 2000; Stevensen 1996). For instance, candles are frequently made with synthetic fragrances and called "aromatherapy." (Buckle 2000).

Essential oils, which contain volatile organic compounds, are extracted from plants, flowers, wood resins, and citrus peels by a process of steam distillation using petrochemical solvents (Buckle 1999). In the past decade, several books have been published that include current research on the chemical constituents and therapeutic actions of each oil. For instance, aldehydes have anti-infectious properties, C10 terpenes have a cortisone-like action, esters have an antispasmodic action, ketones are mucolitic and litholitic, oxides have expectorant and antiparasitic qualities, phenols stimulate the immune system, and sesquiterpenes are antihistamines (Stevensen 1996).

The chemical components found in essential oils have both physiologic and psychologic properties; they work on a molecular level and can be administered in a variety of ways. When inhaled, the nose detects the scent and transmits it to the olfactory bulb, which sends nerve impulses to the limbic system in the brain, including both the amygdala, which controls emotions, and the hippocampus, which stores and retrieves memories. Lavandula angustifolia, for example, an essential oil with sedative and pain relieving properties, is believed to affect the amygdala by increasing inhibitory neurons containing g-aminobutyric acid (GABA); if accurate, this is the same process by which the medication diazepam produces sedation and reduces the effect of external stimuli such as pain. Aromatic chemicals trigger the repository of stored memories in the hippocampus, which can have measurable effects on mood; for example, there are cases of depressed, elderly, institutionalized individuals reporting decreased sadness after smelling certain fruits and flowers that triggered childhood memories. When applied to the skin, essential oils are absorbed into the bloodstream. Occasionally, essential oils are also ingested, but this is considered a component of herbal medicine and should only occur while one is under the guidance of a qualified specialist (Buckle 1999).

In addition to the mechanisms described above, studies suggest that essential oils relieve pain and induce mood changes through several other methods. First, analgesic compounds, such as 1,8-cineole (eucalyptol), activate the brain to release neurotransmitters such as dopamine, serotonin, and norepinephrine. Essential oils such as cardamon, rosemary, and eucalyptus contain eucalyptol. When essential oils are administered topically as part of a massage, the direct touch stimulates sensory fibers in the skin, which triggers the parasympathetic nervous system, thus inducing relaxation and decreasing the perception of pain (Buckle 1999). Essential oils also impact brain wave activity, creating either stimulating or sedative effects (Stevensen 1996).

For topical or inhalant uses, patients may consult professional aromatherapists, as well as nurses, physical therapists, and massage therapists trained in the external use of essential oils; only specially trained professionals can provide treatment for the internal use of essential oils (Buckle 2000). A typical visit includes a discussion of the patient's medical history, presenting complaint(s), and aromatic preferences, as choices of scents are partially based on one's likes and dislikes (Buckle 1999).

Depending upon the condition, patients may be instructed to inhale essential oils either directly by placing a few drops on a piece of cloth, or indirectly through steam inhalations, vaporizers, or sprays. Small quantities (approximately one to five drops) can also be diluted with carrier oils and applied topically in the form of compresses or massage oils. Mixed with milk or cream, they can be added to baths. Some of the therapies may be applied during the clinical evaluation; in most cases, patients also are given instructions on how to continue to use the therapy at home (Buckle 1999).

Scientific literature supports the use of essential oils for insomnia; in addition, several randomized, controlled clinical trials have demonstrated a reduction of pain medication for people with rheumatoid arthritis, cancer, and headaches (Buckle 1999). One randomized, double-blind, controlled trial indicates that thyme, rosemary, lavender, and cedar-wood oils may promote hair growth in people with alopecia areata (Hay et al. 1998); other essential oils improve skin conditions in those with psoriasis (Walsh 1996).

An eight-year clinical trial that collected prospective data from more than 8,000 women who employed aromatherapy during labor and delivery showed promising results. A qualified midwife aromatherapist administered essential oils in the form of inhalations, massages, footbaths, and a drop on the brow or palm during established labor or in the latent phase. The results indicate that rose, lavender, and frankincense oils may reduce feelings of anxiety and fear, improving a women's overall well-being during childbirth, as well as reducing the need for epidural analgesia or other pain medication. Many women report that peppermint oil is effective in relieving nausea and vomiting, common symptoms during labor that frequently are exacerbated by the use of epidural analgesia. Additionally, clary-sage oil may strengthen contractions and decrease the need for oxytocin in women with dysfunctional labor (Burns et al. 2000).

When applied topically, some chemical compounds, including tea tree, have antibacterial and anti-fungal properties (Hay et al. 1998). There is some suggestion in the literature that citrus oils may enhance immune function (Buckle 2000) and that peppermint oil may inhibit the activity of the gastrointestinal smooth muscle, reducing abdominal spasms and digestive disorders (Stevensen 1996). Fennel, aniseed, sage, and clary-sage have estrogen-like compounds that resemble the action of estradiol and balance hormone production, which may make them effective in relieving symptoms associated with premenstrual syndrome, menopause, and the menstrual cycle (Buckle 2000). A randomized, double-blind, crossover study of headache patients treated with topical applications of peppermint essential oil found that the therapy had a significant analgesic effect. In addition, a randomized study of 51 patients with cancer found that massages with chamomile essential oil produced statistically significant reductions in tension, anxiety, and pain (Buckle 1999).

Most of the commonly used essential oils have been tested by the food and perfume industries and hold GRAS (generally regarded as safe) status (Buckle 2000). However, the solvents used in the extraction and distillation processes may cause allergic or sensitizing reactions in certain individuals (Buckle 1999). One occasionally reported side effect is headache (Burns et al. 2000). Although extremely rare, essential oils also have been reported to cause contact dermatitis (Weiss and James 1997). Rare adverse events include abortifacient effects, impaired liver function, and neurotoxicity due to the high quantity of ketones in certain oils, such as Lavandula stoechas (Stevensen 1996).

Given that essential oils contain pharmacologically active ingredients, some may, theoretically, interact with medications, providing either synergistic or negative effects. While this area of study has not been adequately investigated in humans, animal studies indicate that eucalyptol may significantly decrease the effect of phenobarbital and that West Indian lemongrass may potentiate the effect of morphine (Buckle 1999). Other essential oils, such as bergamot, can cause photosensitivity and burns if patients are exposed to sunlight after topical application (Buckle 2000).

Patients should obtain essential oils from reputable suppliers listed with aromatherapy organizations. There can be some adulteration in the production of essential oils (mainly diluting them with cheaper, less effective oils) and the quality of plants can vary depending on the source and growing conditions. In addition, different species of plants vary in terms of potency; therefore, oils should be selected on the basis of the botanical, not the common, name (Buckle 2000).

As mentioned previously, essential oils should never be ingested unless a patient is explicitly instructed to do so by a trained professional; some oils are toxic and taking them orally could be fatal. Oils that are high in phenols, such as cinnamon, can cause dermal irritation. In order to avoid potential reactions, patients should dilute oils before use and avoid using them near the eyes. In addition, essential oils are highly volatile and flammable; they must not be used near an open flame (Buckle 2000).

Patients with hypertension should avoid using stimulating essential oils, such as rosemary and spike lavender (Buckle 1999). Emmenogogic oils, such as hyssop, should be avoided throughout pregnancy; hyssop oil also should be avoided in patients with a history of seizures. In general, all essential oils should be avoided during the first trimester of pregnancy and in patients with severe asthma or a history of multiple allergies. Patients with estrogen-dependent tumors should not use oils with estrogen-like compounds such as fennel, aniseed, sage, and clary-sage. Practitioners should exercise caution when using essential oils with patients undergoing chemotherapy (Buckle 2000).

Although more research is required, there are anecdotal reports of the successful use of essential oils to treat acne, anorexia, anxiety, autism, borderline hypertension, bronchitis, burns, chronic pain, constipation, cystitis, depression, diabetic ulcers, idiopathic infertility, indigestion, insomnia, irritable bowel syndrome, low back pain, memory loss, migraines, mild asthma, muscle pain, nausea, orthostatis, osteoarthritis, premenstrual syndrome, psoriasis, sinusitis, sports injuries, staphylococcal skin infections, stress, substance abuse, water retention, and bacterial, viral, and fungal infections. In addition, children with autism, behavioral problems, colic, diaper rash, and sleep problems may benefit from the nonverbal stimuli of smell and touch, which facilitate communication at a basic level. Essential oils also may be an effective adjunct modality for problems affecting the elderly, such as memory loss, dry skin, bed-sores, and Alzheimer's disease (Buckle 2000). Research on mice suggests that sandalwood decreases skin papillomas (Hay et al. 1998).

Although essential oils have been used for millennia, few controlled clinical trials have been conducted in human beings. While there are many potential uses of aromatherapy in a wide variety of settings, conclusive evidence of its clinical efficacy is lacking (Buckle 2000). Additionally, there are some concerns regarding the safety and quality of certain essential oils (Stevensen 1996). More research is necessary before aromatherapy becomes a widely accepted alternative modality with clear and specific clinical indications (Buckle 2000).

Training courses to become an aromatherapist generally range from one weekend to several years; there are no prerequisites prior to participating in the curriculum and there is currently no licensing procedure. People who take the courses tend to be massage therapists, registered nurses, and physical therapists. At present, there is no recognized national certification examination, although Educational Standards in Aromatherapy in the United States is in the process of establishing the Aromatherapy Registration Board as a nonprofit governing body that will administer a national standardized exam and provide the public with a list of registered practitioners (Buckle 2000).

For a directory of aromatherapy schools and practitioners, contact the National Association for Holistic Aromatherapy, P.O. Box 17622, Boulder, CO 80308, 888-ASK-NAHA, www.naha.org. The trade association that publishes the quarterly Journal of Aromatherapy is the American Alliance of Aromatherapy, P.O. Box 750428, Petaluma, CA 94975-0428.

Certification courses are offered by the American Aromatherapy Association, P.O. Box 3679, South Pasadena, CA: Aromatherapy Seminars, 3379 South Robertson Blvd., Los Angeles, CA 90034; The Pacific Institute of Aromatherapy, P.O. Box 6842, San Rafael, CA 94903.

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Burns EE, Blamey C, Ersser SJ, Barnetson L, Lloyd AJ. An investigation into the use of aromatherapy in intrapartum midwifery practice. J Altern Complement Med. 2000;6(2):141-147.

Hay IC, Jamieson M, Ormerod AD. Randomized trial of aromatherapy: successful treatment for alopecia areata. Arch Dermatol. 1998;134:1349-1352.

Stevensen CJ. Aromatherapy. In: Micozzi MS, ed. Fundamentals of Complementary and Alternative Medicine. New York, NY: Churchill Livingstone Inc.; 1996:137-148.

Walsh D. Using aromatherapy in the management of psoriasis. Nurs Stand. 1996;11(13-15):53-56.

Weiss RR, James WD. Allergic contact dermatitis from aromatherapy. Am J Contact Dermat. 1997;8(4):250-251.