MEDICAL AROMATHERAPY

This is also known as aromatic medicine or aromatology. It is used in France and increasingly in the UK, and there is growing interest in Australia. An education program encompassing the internal use of essential oils was recently approved by the Australian National Training Authority. Medical aromatherapy utilises the internal administration of essential oils via the oral, rectal and vaginal routes, as well as in dressings, ointments and fumigation. Only steam-distilled and expressed essential oils are used internally. In France prescribing for internal use is regulated and restricted to medically qualified doctors who have the relevant training. A pharmacist often formulates the prescriptions. Aromatherapists may work under the direction of a doctor. In some other countries, other practitioners can prescribe essential oils if they have the relevant qualifications.

SUBTLE AROMATHERAPY OR AROMACOLOGY

This is the German model of practice, which largely uses inhalation to influence psychological and spiritual states.

POPULAR, OR TRADITIONAL, AROMATHERAPY

Largely based on the UK model, this involves inhalation and massage. Touch, an essential aspect of massage, has its own health benefits, and this model uses topical application in massage, gels, creams and lotions, as well as inhalation for physical, psychological and spiritual effects. There are two subgroups: therapeutic aromatherapy, which is used in healthcare, and cosmetic or beauty care aromatherapy. Australian aromatherapists largely follow the UK model, but some incorporate aspects of all three models.

All three models use essential oils as the main medicinal substance. Essential oils are rarely used undiluted, but rather are incorporated into various carrier substances, depending on the administration/application route. Most aromatherapists formulate blends for individual patients, but fixed-formulation blends are available: for example, massage blends for pain relief. Aromatherapy is very popular with the general public and self-prescribing by following the directions in self-care books, magazine articles and short education courses is common. In Australia some health insurance funds reimburse the costs of aromatherapy treatments, provided the aromatherapist is qualified through an approved training facility.

CHEMISTRY

Essential oils are secondary plant metabolites and are complex chemical compounds that have a different composition from the herb extract of the same plant. Essential oils are stored in specific secretory structures in leaves, twigs, seeds, petals, bark and roots, often with resins and gums in oil cells, sacs, resin canals, ducts and hairs, and are extracted from these structures by steam distillation, expression, enfleurage, solvent extraction, maceration and more recently supercritical carbon dioxide extraction, depending on the plant source (Guba 2002, Price & Price 1995). More than 3000 odour molecules have been identified.

Chemical variations are common in plants of the same genus and these are known as chemotypes. The best known chemotypes occur in the essential oils of Thymus vulgaris (thyme), Rosmarinus officinalis (rosemary), Ocimum basilicum (basil), and Melaleuca alternifolia (tea tree). Growing conditions, harvesting, storage and handling are known to affect the chemical composition of essential oils (Guba 2004, Price & Price 1995). Common phytochemicals in essential oils are terpenes, sesquiterpenes, alcohols, phenols, aldehydes, ketones, esters, acids, phenolic ethers, oxides, lactones and coumarins (Bowles 2003, Clarke 2002). It is necessary to understand the chemical composition of essential oils in order to understand their application in healthcare and the safety aspects associated with their use.

Of the many chemicals present, the alcohols, lactones, phenols and sesquiterpenes are considered to have a major impact on the odour of the oil and are of particular significance in the cosmetic and perfumery applications of aromatherapy. Of these chemicals, alcohols are considered to be among the most important for therapeutic effect and pleasant fragrance. They often have antimicrobial properties and low toxicity, and are described as warming, uplifting and good general tonics. Two examples of alcohols found in essential oils are:

The sesquiterpenes consist of three isoprene units and make up the largest group of terpenes found in the plant world. They tend to have strong odours and a variety of pharmacological effects. Two examples of sesquiterpenes found in essential oils are:

Optical isomerism also influences the odour of a substance, so two different oils containing the same specific chemical may have different odours because the chemicals are stereoisomers. For example, d-limonene found in citrus oils, pine leaves and peppermint has a citrus odour, whereas its stereoisomer l-limonene has a turpentine-like odour and is found in citronella and lemon verbena.

Although the pharmacological effects of many of the constituents found in essential oils have not yet been fully investigated, a few that have been investigated are notable for their significant activity. For example, eugenol is a phenol found in cinnamon, oil of cloves and ylang ylang, giving the oils a spicy, pungent odour and significant antimicrobial activity. Cinnamaldehyde, chiefly found in cinnamon oil, has also been well investigated. It has antispasmodic, antimicrobial and fungicidal activities and is described as having a warm, spicy and balsamic odour.

Most of the essential oils produced are used in the food, cosmetic and, to a lesser extent, medicine industries, where strict composition standards are needed to ensure products meet relevant standards. Organisations such as the International Organisation for Standardisation (ISO), Research Institute for Fragrance Materials (RIFM), International Fragrance Association (IFRA) and Association Française de Normalisation (AFNOR) have developed composition standards for many essential oil products used in the food and perfume industries, and this is an important aspect of quality control. The ISO and AFNOR standards are often accepted as the most reliable indicators of quality.

The need to achieve compositional consistency has led some manufacturers to artificially manipulate chemical composition, using adulteration, substitution and rectification, to ensure essential oils meet the standard and to reduce the cost of expensive oils such as rose and jasmine. Plant conservation issues have also affected aromatherapy practice: for example, the sale of essential oils from some endangered species is banned in Europe. In some cases synthetic products have been developed, which may increase the potential to cause adverse events and bring aromatherapy into disrepute. The European Federation of Essential Oils was formed in 2002 to increase awareness of the need for sustainable harvesting to benefit both local communities and aromatherapy, as well as to conserve endangered plants.

Analytical techniques such as gas chromatography, mass spectrometry, infrared spectroscopy, optical rotation and refractive index are used to assess the composition and purity of essential oils. Frequently mass spectrometry and infrared spectroscopy are considered together. The analytical information, together with other safety information, is detailed in material safety data sheets, which are available from essential oil suppliers and manufacturers. More recently, the cosmetic industry has begun to examine the peroxide value (POV) of both essential and fixed vegetable oil carrier oils. POV is an indicator of the potential of an essential oil to cause skin irritation and sensitivity (Wabner 2002). In addition, the physical appearance (colour and consistency) and odour of the oil are important aspects of quality.

Currently, there is not a standard for ‘therapeutic-grade essential oils’ (Guba 2004). However, some suppliers undertake independent quality-control tests to ensure essential oils meet aromatherapy requirements and to guarantee that their essential oils are:

In Australia most essential oils are listed in schedule 14 of the medicines scheduling system of the Therapeutic Goods Administration (TGA). However, TGA listing does not necessarily indicate benefit or efficacy, but does indicate that the risks associated with listed products are low. Manufacturers are not permitted to make therapeutic claims for listed products.

Aromatherapists prefer to use the entire essential oils rather than isolated compounds or synthetic oils, because the chemicals present in individual essential oils and blends have synergistic and quenching properties that enhance the beneficial effects and reduce unwanted effects. These beneficial interactions occur among the individual constituents within an oil and among the essential oils in a blend of oils (Clarke 2002, Price & Price 1995, Opdyke 1976). In most cases a blend of essential oils is used to suit the condition being treated, and the composition of the blend is modified according to the individual’s response in much the same way as herbal medicines are used. Common application/administration methods and doses are shown in Table 4.2 at the end of this chapter. Recommended doses are based on a long history of traditional use and the recommendations of experts, rather than on dose-finding trials. A number of factors need to be considered when deciding on an application method, dose and dose interval including:

Most aromatherapists do not recommend using fragrant oils for therapeutic purposes, although most accept they may have a role as environmental fragrances and may have psychological effects.

CARRIER SUBSTANCES

In most cases essential oils are dispersed in another substance known as a carrier. Carrier substances for massage are usually cold-pressed or fixed vegetable oils, such as sweet almond, grapeseed and macadamia nut oil, depending on the aims of treatment. In massage, the carrier oils primarily provide lubrication for the therapist’s hands to allow smooth movement over the skin and to enhance absorption of the essential oils; however, some fixed oils, such as those of calendula (Calendula officinalis) or St John’s wort (Hypericum perforatum), also have therapeutic properties.

Other carriers include honey, Aloe vera, shea and cocoa butter, and waxes, which are used for capsules, ointments and suppositories intended for internal use. Purified clays such as bentonite are also used as carriers for essential oils to be applied in compresses, poultices and face and body masks/packs in beauty care. Incipients (dispersants) are usually required if essential oils are added to water to keep them in solution because essential oils are generally insoluble in water.