Aromatherapy encompasses the use of essential oils derived from different types of plant sources for a variety of application methods. Generally, the whole fresh plant (not crushed or powdered) is used for the essential oil distillation process. The specific ingredients of an essential oil are derived from plant materials or parts that are claimed to possess therapeutic properties. Essential oils are “the steam distillate of aromatic plants” (Tisserand and Balacs, 1995
). They have been described as “the volatile, organic constituents of fragrant plant matter and contribute to both flavor and fragrance and are extracted either by distillation or by cold pressing (expression)” (Tisserand and Balacs, 1995
). The history of distillation of essential oils started with the medieval physician Avicenna (Abu Ali al-Hussein Ibn Abdallah Ibn Sina; 980 – 1037) from Persia who invented the process of distillation and was probably the first to distil oil of the rose plant (Tisserand, 1988
). Today, approximately 40 different oils derived from plants are used in aromatherapy. Lavender, rosemary, eucalyptus, chamomile, marjoram, jasmine, peppermint, lemon, ylang ylang, and geranium are some of the most popular.
The term ‘aromatherapy’ was coined by French chemist and perfumiér René Maurice Gattefossé in the 1920s and is a subcategory of ‘herbal medicine’ (Gattefosse, 1993
). Gattefossé's book was published in 1937. He suggested that aromatherapy could be used to treat diseases in virtually every organ system, citing mostly anecdotal and case-based evidence. In the 1960s, aromatherapy was revived by the French homeopath Dr. Maury, and in the 1980s it increased in popularity in the United States. It is fairly well-established in Australia, Canada, France, Germany, New Zealand, Switzerland and the UK.
There are various forms of application. Most commonly, oils are applied topically in diluted forms, often together with a carrier oil as part of massage therapy to manipulate the soft tissue of the body, or by using an incense burner for inhalation of the aroma. Essential oils may be inhaled by adding a few drops to steaming water, thereafter an atomizer or humidifier spreads the aroma throughout the room. Certain aromatherapy oils are also ingested through teas, whereas others can be added to bathwater or pillows, or used to make ointments, creams and compresses. Some aromatherapists argue that the use of certain herbs in food can also be considered part of aromatherapy, although this should be considered as a specific alimentation rather than a precise use as essential oils.
Essential oils are supposed to improve physical and emotional wellbeing (www.cancer.gov/cancertopics/pdq/cam/aromatherapy/healthprofessional.page1
). A wide range of claims for the effect of certain oils have been put forward, ranging from: to affect a patient's “subtle body”; bring balance to a distinct “chakra”; restore harmony to the “energy flow”; become centered; contribute to “spiritual growth”; alter mood and improve overall health; to more specific claims such as having anticonvulsive and spasmolytic properties (www.skepdic.com/aroma.html
). It has been suggested that the topical application of aromatic oils may exert antibacterial, anti-inflammatory, and analgesic effects.
For cancer patients, claims of benefits include reduced anxiety levels and relief of emotional stress, pain, muscular tension and fatigue (Fellowes et al, 2004
). Some of these alleged outcomes are vaguely defined.
The chemical properties and composition of a specific type of oil gives it whatever therapeutic qualities the essential oil might have. A number of theories try to explain the mechanism of action of aromatherapy and essential oils. The most often cited is the proposed connection between olfaction and the limbic system in the brain as the basis for the effects of aromatherapy on mood and emotions (Smith, 1999
). These assertions have been contested by the biochemistry and psychology communities, which take a different view of the possible mechanism of action of odors on the human brain and do not differentiate the odors produced by essential oils from those of synthetic fragrances (Perry and Perry, 2006
). Little is said about proposed mechanisms for its effects on other parts of the body. Unfortunately, many of these assumptions are primarily theoretical because of the lack of significant research addressing this topic. There is also a lack of in-depth neurophysiological studies on the nature of olfaction and its link to the limbic system.
An individual's expectation and subjective perception of oil supposedly influences treatment outcomes, including whether or not an individual has previous experience with a particular scent and whether it is perceived as pleasurable (www.sirc.org/publik/small.pdf
). Marked association of odors with emotional response has been shown to be due to the prominence of afferent links from the olfactory bulb to the amygdala, where emotional significance is attached to incoming stimuli (Clark and Boutros, 1999
Neuro-chemical aspects involve a suggested inhibition of glutamate binding, γ-amiobutyric acid (GABA) augmentation and acetylcholine receptor binding. As an example, the main terpenoid component of lavender oil is linalool. Linalool has been shown to inhibit glutamate binding in rats (Watt, 1995
) and inhaled lavender oil reduces electroshock-induced convulsions in mice, which suggests augmentation of GABA (Yamada et al, 1994
). Linalool's inhibitory effect was demonstrated to be dose dependent with increasing concentrations; all response was abolished by the use of 6.5 mM linalool. This modifying effect on the glutamatergic system is comparable with phenobarbital, a known anticonvulsant (Elisabetsky et al, 1995
). Further evidence for this mechanism comes from the finding of a potentiation of GABA receptors expressed in Xenopus oocytes by lavender oil components (Aoshima et al, 2001
It has been suggested that compounds from essential oils may enter the body (via the olfactory mucosa or the bloodstream by lung absorption) and may directly influence the brain (Watt, 1995
). It is suggested that there are scent receptors in the nose which send chemical messages via the olfactory nerve to the brain's limbic region. This in return can affect a person's emotional responses, heart rate, blood pressure and breathing.
Generally speaking, the application of aromatherapy is suggested to help patients cope with stress, chronic pain, nausea and depression. One can assume both direct effects of the oils, but also positive expectations of the patients. Furthermore it has been suggested that the use of essential oils can relieve bacterial infections (Geda, 1995
), stimulate the immune system (Komori et al, 1995
), help to fight colds, flues and sore throats (Hasani et al, 2003
), improve urine production (Morimoto and Shibata, 2010
), increase circulation (Shiina et al, 2008
) and aid in the healing of cystitis (Eriksen, 2000
), herpes simplex (Buckle, 2002
), acne (Eriksen, 2000
), headaches (Eriksen, 2000
), indigestion (Schnaubelt, 1999
), premenstrual syndrome (Eriksen, 2000
), muscle tension (Lis-Balchin et al, 2000
), and even cancer (Fellowes et al, 2004
). Specific indications can only be discussed by choosing a selected number of essential oils.
In Australia, three surveys showed that up to 1% of cancer patients used aromatherapy (Girgis et al, 2005
, Salminen et al, 2004
, Correa-Velez et al, 2003
). In Canada, two surveys revealed that up to 4% of cancer patients used it (Tough et al, 2002
, McKay et al 2005
). In Italy, Spain and Turkey prevalence ranges from <1 to 2% (Johannessen et al, 2008
, Fernandez-Ortega et al, 2008
, Akyuz et al, 2007
). In contrast, six surveys carried out in the UK showed that 40.6% of cancer patients were using it (Lewith et al., 2002
, Maher et al., 1994
, Rees et al., 2000
, Harris et al., 2003
, Scott et al., 2005
, Shakeel et al., 2008
). A US survey revealed that 11% of cancer patients may be using aromatherapy and in New Zealand 6% (Lawsin et al., 2007
, Chrystal et al., 2003
). However, it is unclear whether this usage is a specific anti-cancer intervention or simply to increase general well-being and thus life-style associated rather than a therapeutic approach. One could assume that a similar percentage of healthy individuals is using essential oil, too.
Since aromatherapy can also be applied orally or rectally, the administration of such oils may not be legally permitted in several countries, unless it is applied by a medically qualified person. There may be legal issues resulting from the fact that diluted essential oils can “penetrate the skin”, which could be considered as administering a drug. This review was carried out as a project for the European CAM cancer consortium (www.cam-cancer.org
) and includes studies which assess the effect of aromatherapy on its own or in conjunction with massage therapy. The objective of this paper is to provide an updated review of evidence from pre-clinical and clinical trials assessing the benefits and safety of aromatherapy for cancer patients.