3 (Part II) Power and hazards
This term includes irritation, phototoxicity and sensitization. To minimize risk it is important to bear in mind that essential oils must be properly sourced, of the highest quality, botanically identified, well stored and unadulterated (many cases of dermal toxicity can be traced back to substances that have been added for commercial reasons). Steam distilled essential oils are superior to other extracts such as absolutes, concretes, carbon dioxide extracted etc.; lavender absolute was involved in two cases, one a therapist with a 3-year history of dermatitis extending to the face and neck (Bleasel, Tate & Rademaker 2002).
This is a reaction to a substance that produces inflammation and itchiness. Some essential oils are irritating to the skin, and these are usually (but not exclusively) found to contain high proportions of either aldehydes or phenols. Oils in common use which have been found to be irritant are listed in Appendix B.6 (see CD-ROM). Because there appear to be wide variations in tolerance, a given oil might not cause a reaction in the majority of people yet be irritant to one or two more sensitive individuals; dermal irritation produced by essential oils is usually localized and short lived. Assuming that one oil has a 50% presence of an offending component, this is present in the total mix at only 0.5% when the oil is used in a normal massage mix along with two or three other oils at the standard dilution of 3% essential oils in a carrier.
When spread over a large area of skin the possibility of irritation is remote; the degree of irritation is proportional to the strength of the mixture applied.
The following oils have been recorded as being implicated in irritation:
Tagetes – an aromatherapist presented with acute bilateral hand eczema 24 hours after spraying roses with an insecticide and patch testing gave a strong reaction to Tagetes patula [French marigold]; the acute eczema was attributed to a cross-reaction with pyrethroid in the insecticide (Bilsland & Strong 1990). Dermatitis caused by the leaves and flowers of Tagetes minuta, T. patula, T. erecta and T. glandulifera is common in South Africa, and the essential oil of Tagetes glandulifera is sometimes cited as being a skin irritant, but we have not found this to be the case in practice, although it is a photosensitizer.
Brassica nigra [mustard] and Armoracia rusticana [horseradish] – two oils from the Cruciferaceae family which are not normally recommended for aromatherapy use because both consist almost entirely of allylisothiocyanate. These oils applied neat to the skin will provoke severe burning and blistering, but it has been known for them to be recommended at the extremely low concentration of one drop of essential oil in 500 mL of carrier oil for rheumatism.
Melaleuca alternifolia – there are many cases reported of skin irritancy and dermatitis involving tea tree oil (Bhushan & Beck 1997, Southwell, Freeman & Rubel 1997). It should be borne in mind that tea trees are cultivated, grown from seed, and therefore the composition of the oil when distilled is variable. This oil is then adjusted at source to conform to laid down parameters (especially the 1,8-cineole content) and so may not have the natural synergy that may be expected. Tea tree oil has a relatively simple composition (about 30 compounds). Some oils are synthesized in a laboratory and are known as reconstructed oils (RCO); they are not natural products and may have unwanted side effects. Seven people had been applying commercial tea tree oil undiluted on the skin for conditions such as fungal infections, pimples and skin rashes, and all developed eczematous dermatitis, some with vesiculation; a common allergen was (−)-limonene: the application of diluted oil to the skin caused no reaction (Knight & Hausen 1994), showing that use of the commercial oil undiluted was ill advised. Treatment of chronic atopic dermatitis by application of undiluted Melaleuca alternifolia was unsuccessful and then oral ingestion of the oil mixed with honey was advised, which led to exacerbation of the dermatitis; 1,8-cineole was the allergen (De Groot & Weyland 1992). The reasoning behind this treatment is hard to understand.
Santalum album [sandalwood] – overdose due to daily application for 8 years of sandalwood paste to the forehead led to a hyperpigmented, erythematous plaque and lesions and fissures on thumb and forefinger; sandalwood paste patch test proved positive (Sharma, Bajaj & Singh 1987). The offending compound was not identified.
Pimpinella anisum [aniseed], Syzygium aromaticum flos, fol., caul. [clove, bud, leaf and stem] can irritate the skin if used in high concentration because of their phenolic ether and phenol content, respectively.
Cinnamomum verum cort., fol. [cinnamon bark and leaf] – the bark oil contains cinnamal, which is a known skin sensitizer, but the whole oil proves to be less so. A patch test should always be carried out prior to using this oil.
Of 1500 dermatitis patients who were patch tested, 21 had a reaction to essential oils (which were not botanically specified) of pine needle, dwarf pine, clove and eucalyptus, and it was found that some components of the essential oils – carene, phellandrene and eugenol – were sensitizers (Woeber & Krombach 1969). The regional provenance of the essential oils had no great influence on sensitization potency: good quality and lack of ageing were more important. A therapist with a 3-year history of forearm dermatitis was sensitive to a range of oils containing geraniol but was also sensitive to yarrow, laurel and peppermint oils, which do not contain geraniol (Bleasel, Tate & Rademaker 2002).
More than 95% of users of essential oils in aromatherapy are women, hugely outnumbering men: perhaps it is relevant that a Japanese study showed that the skin of men tends to be more than twice as sensitive as that of women, and that in situations of severe stress, lack of sleep, etc. all skins are rendered more sensitive (Hosokawa & Ogwana 1979).
Generally speaking, essential oils with a substantial content of phenols (chiefly thymol, carvacrol and eugenol) can be responsible for irritating a mucous membrane. Oils containing aldehydes may also be implicated. In the past it was believed that the hydrocarbon terpenes caused mucous membrane irritation (Gattefossé 1937 p. 40) but this is now thought not to be the case. Any of the oils listed in Appendix B.6 (see CD-ROM) may cause irritation of the mucous membranes of the alimentary, respiratory and genitourinary tracts. A possible exception is lemon oil, which contains less than 5% aldehyde and consists mainly of hydrocarbon terpenes, principally (+)-limonene, which is known to quench the irritant effect of the aldehyde.
There are some oils that do not produce any reaction on first contact with the skin but may do so on a subsequent application; there seems to be no common denominator to those essential oils that are sensitizing. The body’s reaction involves the immune system, via the cells in the basal layer of the epidermis. Poor storage of oils containing a significant amount of monoterpenes can lead to the formation of sensitizing hydroperoxides: an infamous example is turpentine, which is responsible for skin allergies in workers in the paint industry. Oils to be wary of in this respect are shown in Appendix B.8 (see CD-ROM).
Once a person is sensitized to one substance, that person is more likely to be susceptible to other similar substances, although the risk is low. This need not cause concern, but any aromatherapist who is sensitive to substances should be aware of the possibility. This is a complex topic, not well understood, but one example is that people can become sensitive to benzoin after sensitization to Peru balsam or turpentine. There is a similar relationship between turpentine and peppermint, and a case of turpentine-induced sensitivity to peppermint oil involved a laboratory technician who suffered swelling of tongue, lips and gums after a dental operation. Tests revealed sensitivity to peppermint oil, an ingredient in dental spray and mouthwash, and this was due to α-pinene, limonene and phellandrene, which are also present in turpentine, from which he had previously developed severe eczema of the hands (Dooms-Goossens et al. 1977): Cymbopogon martinii [palmarosa] is implicated in cross-sensitization with lavender, lemongrass and geranium.
An aromatherapist had a 12-month history of hand and forearm dermatitis which improved when away from work. Patch testing revealed positive reactions not only to oils of lavender, geranium and lemongrass, but also to oils to which she had not been previously exposed (palmarosa, frankincense, rose, neroli, myrrh), which implied cross-reactivity (Bleasel, Tate & Rademaker 2002). Dermatitis recurred after eating lemongrass- flavoured food – systemic contact dermatitis.
A man allergic to turpentine breathed in the vapour of tea tree oil in hot water to help his bronchitis and developed acute exudative dermatitis of the face, trunk and arms (De Groot 1996). The origin of the essential oil was not stated. A woman who had been treating her acne for a long time with undiluted Melaleuca alternifolia [tea tree] essential oil without reaction presented with dermatitis on her forehead and mouth: patch testing was positive to tea tree and colophony (an oleo resin from which turpentine is distilled): crossreaction between turpentine and colophony had already been established (Selvaag, Erikson & Thune 1994). Palmarosa has been implicated in cross sensitization with lavender, lemongrass and geranium (Dooms-Goossens et al. 1977 p. 73), and galbanum resin has been linked in cross-sensitization with Peru balsam (see also Appendix B on the CD-ROM).
Photosensitization is a process in which reactions to normally ineffective radiation are induced in a system by the introduction of a radiation-absorbing substance – the photosensitizer (Kochevar 1987). Photosensitivity may occur when certain essential oil components, particularly the expressed essences, react with the skin under the influence of ultraviolet rays, yet does not occur on skin protected from natural or artificial sunlight. It may result in erythema, hyperpigmentation and perhaps vesicles, depending on the severity of the reaction. Furanocoumarins (psoralens) appear to be primarily responsible for phytophototoxic reactions in humans (Lovell 1993), so care needs to be taken with the citrus essences, which are expressed from the peel and contain furanocoumarin molecules, particularly bergamot. Other oils exhibiting this characteristic at aromatherapeutic doses are Angelica archangelica rad. [angelica root], Juniperus virginiana [Virginian cedarwood], Ruta graveolens [rue], Lippia citriodora [lemon verbena] and Cuminum cyminum [cumin] (Opdyke 1974) (see Appendix B.7 on the CD-ROM).
Factors that influence the phototoxic response to psoralens are the presence of a suntan, natural pigmentation (dark skin), site of application, skin hydration, and the interval between application of the psoralen and irradiation (it is worth mentioning that aromatherapy oils are applied mainly to areas not normally exposed to sunlight). A particularly notable culprit is the expressed oil of Citrus bergamia [bergamot] (Opdyke 1973), which was studied by Zaynoun, Johnson and Frain-Bell (1977), and its use in aromatherapy needs consideration; tests by Pathak and Fitzpatrick (1959) have shown the time interval between applying psoralens and the maximal phototoxic effect to be 30–45 minutes (tested on guinea pig and human skin), and a later test (Arora and Willis 1976) indicated a time interval of up to 75 minutes.
Tests probably carried out for the benefit of the perfumery trade on bergamot oil in ethyl alcohol showed no phototoxic responses at a concentration of 0.5%, and at 1.0% no phototoxic response after 8 hours; the tests were carried out on five subjects (Zaynoun, Johnson & Frain-Bell 1977 p. 231) and also showed that intervals of 1–2 hours between application and irradiation yielded a maximal phototoxic response. Applying this directly to aromatherapy is questionable, as aromatherapists do not use ethyl alcohol as a medium for application, and the flow of psoralen through the horny layer of the skin is dependent on the carrier used (Kaidbey & Kligman 1974, Kammerau et al. 1976). It is known that the horny layer is a major barrier to the penetration of psoralens; in tests, 70–90% of topically applied 8-methoxypsoralen (8-MOP, xanthotoxin, which is not present in bergamot oil) did not enter the horny layer and was finally lost through sloughing (Kammerau et al. 1976). Bergamot oil itself is resorbed through the skin in 40–60 minutes (Römelt et al. 1974, Valette 1945).
The tests by Zaynoun, Johnson and Frain-Bell (1977 p. 232) also showed that using paraffin molle flavum (PMF) as the carrier resulted in increased speed of penetration through the horny layer and produced a shorter period in which phototoxicity persists than when using ethanol, and it is possible that the effects using a vegetable oil as a carrier more closely resemble the results using PMF than those using alcohol.
The IFRA Committee recommends a level of 5-MOP (bergapten, a naturally occurring analogue of psoralen) of 75 ppm in a (fragrance) compound, and assuming a 5-MOP content of 0.35% this equates to a level of expressed bergamot oil in the compound of 2% (Jouhar 1991), which translates to 0.4% (about eight drops in 100 mL) in an aromatherapy preparation applied to skin. The use of 5-MOP is forbidden in the EU except as a normal component of essential oils.
In practical experience over four decades, there has been no reported problem by thousands of therapists who have followed our training and numerous clients who have followed our advice. On this basis, it is suggested that following the application of bergamot oil using the normal aromatherapy dilution (usually less than 1% in synergistic blends) it is reasonably safe to expose the skin of normal people to sunlight provided that more than 2 hours have elapsed since the application. This advice may be tempered in case of any unusual sensitivity in the individual client. It is interesting to note that some other simple coumarin derivatives, such as umbelliferone, herniarin and aesculetin, have a sunlight filter effect because they absorb ultraviolet light of 280–315 nm (Schilcher 1985 p. 228).
It is necessary to be wary of reported cases now that the fragrance industry relies so heavily on synthetic materials. An example is a middle-aged man who used a sandalwood aftershave lotion for 3 weeks which brought about weeping, lichenified dermatitis of the face which worsened in sunlight, even after discontinuing the aftershave lotion. On analysis the commercial sandalwood was found to be composed of synthetic and natural geranium, synthetic and natural sandalwood, cedarwood oil and patchouli oil; he tested positive to both synthetic and natural geranium.
If any one oil is used for a very long period there may be a risk of sensitization even though none exists in normal usage. When eau de Cologne (which contains bergamot and other citrus essences) was much in vogue many people wore it daily over a period of years and developed raised erythematous rough skin where the eau de Cologne had been applied – usually on the neck (berloque dermatitis). This reaction can be semi-permanent, lasting for years after fragrance use has ceased before disappearing (Shirley Price’s personal experience). Many perfumes have ingredients in common with eau de Cologne and may produce similar reactions. A 47-year-old woman who sold food that was smoked and spiced with juniper berry oil, had for 25 years had a rash that had become generalized, followed by a dry cough and asthma; skin tests with juniper and pine oils proved positive (Rothe, Heine & Rebohle 1973).
Melaleuca alternifolia [tea tree] oil was identified as a possible cause of relapsing eczema in a 53-year-old woman who had prolonged exposure to the oil (Schaller & Korting 1995). She was also allergic to other essential oils, including lavender, jasmine and rosewood, which may also have resulted from prolonged exposure to the oils, but she was in addition allergic to laurel and eucalyptus, to which she had not been previously exposed. This report emphasizes the importance of treating essential oils with respect, especially when using them for prolonged periods. It is good aromatherapy practice to change the oils used during a treatment of long duration.
A survey carried out (Wong 1995) on the personal effects on 120 aromatherapists using essential oils in treatments revealed that they occurred on many levels. A few therapists suffered adverse effects, but it was felt that these were due to reactions to clients rather than to the oils themselves. It is emphasized that this was a survey, not a properly constituted trial. Of the 120 therapists surveyed:
• most felt the effects were beneficial
• most had been in practice for less than 4 years
Effects on particular systems included the following:
• 105 therapists experienced insignificant or no effect.
• Several experienced skin irritation, often between the fingers, and sweet almond oil and geranium were mentioned by two therapists as the offenders.
• Two therapists appeared to have developed eczema, and previous dermatitis in one had disappeared.
• About 28% of the women surveyed felt some effect on their reproductive system, but most did not know whether this was due to the essential oils or to other factors.
• Some said they felt no effects when using oils on clients, but experienced considerable effects when using oils on themselves.
• Most experienced positive effects such as an improvement in PMS, period pains and menopausal symptoms, and a more regular menstrual cycle. Salvia sclarea [clary sage] was mentioned many times in this context.
• Six aromatherapists had been pregnant while practising; some found their sense of smell became more acute and they could not tolerate strong aromas.
• A few therapists felt adverse effects such as tender breasts, irregular or heavy menstruation, a change in menstrual cycle and fluctuating hormone levels, but these are common and may not be linked to essential oil use.
Note that the quality of the oils used by those surveyed is unknown, and it is known that synthetics added to essential oils have effects of their own. In a general survey such as this other circumstances may well have had an effect, e.g. diet, medication, general state of health, allergies etc.; the performance of the massage itself may be responsible for some of the joint and circulation problems reported.
Unwanted effects are rare and mostly following overdose or overuse. The general safety of essential oils normally used in aromatherapy may be judged by the health of workers who handle and inhale significant quantities in the course of their daily work. Some members of our own staff handled, bottled and breathed a wide range of oils during the whole of their working day for over two decades with no reported bad effects. There are many therapists (including ourselves) who have been working full-time with the oils for over three decades who have experienced nothing but good effects, and it may therefore be inferred that aromatherapy is basically safe. There are one or two therapists who have developed sensitivity to a few oils; unfortunately, if the sensitivity is due to a specific molecule in the oil, then wherever it occurs the person may have a reaction; in some cases a reaction may be due to an adulterant rather than a natural component of the essential oil. Therapists who do not use perfumes run less risk of developing sensitivities to essential oils, as the overall quantity of synthetics employed in perfumes in day-to-day situations plays a large part in the growing number of people developing allergies and substance sensitivities (Bennett 1990).
There is no available evidence that any natural essential oil has ever provoked mutagenicity or teratogenicity in an embryo or developing fetus. No tests have been carried out because the possibility of fragrant materials causing either genetic mutation or malformation is regarded as unlikely.
A few oils have been tested for carcinogenicity on animals and the essential oil components safrole and dihydrosafrole have been implicated in the formation of hepatic tumours in rats; calamus oil containing β-asarone produced duodenal tumours (Taylor et al. 1967). For this reason, sassafras, which contains safrole as an important constituent, is not used in aromatherapy. Safrole is significantly present in Brazilian sassafras oil and in trace amounts in white camphor oil. Wiseman et al. (1987) found that β-asarone produced malignant liver tumours in rodents, but another study failed to confirm the carcinogenicity of β-asarone and calamus oil in rats (Ramos-Ocampo 1988). β-Asarone (found in calamus oil) is restricted in foods and drinks to 0.1–1 mg/kg.
Despite some evidence from animal testing (where the doses used were large), it is thought that there is minimal risk in humans undergoing aromatherapy treatment; Tisserand and Balacs (1995 p. 101) suggest that a safe level for external use in aromatherapy is 0.1% maximum of β-asarone (also estragole, methyl eugenol and safrole).
Special care must be taken with a few essential oils containing significant amounts of a ketone, which can be aggressive to nerve tissue. Not all ketones are neurotoxic (Winter 1999 p. 113), but as a class they must be regarded as hazardous in this respect. Particular care must be exercised when using oils containing apiole (e.g. Petroselinum sativum (fruct.) [parsley seed]) and ascaridole (e.g. Peumus boldus [boldo]). (For the risks of using neurotoxic oils in pregnancy see Ch. 12.) The molecules in essential oils are lipid soluble and as such can pass the blood–brain barrier and access the central nervous system. The degree of lipid solubility varies from one class of molecule to another: e.g. esters are more fat soluble than are alcohols. Once past this barrier there is a potential for toxicity: an accidental overdose of Syzygium aromaticum [clove] (5–10 mL) produced convulsions in a child (Hartnoll et al. 1993). It is thought that the ketone thujone found in Thuja occidentalis, Tanacetum vulgare, Artemisia vulgaris and A. absinthium is toxic to the central nervous system, as is the ketone asarone (found in Acorus calamus) (Wenzel & Ross 1957).
When using essential oils having appreciable quantities of aldehydes there is a risk of toxicity due to build-up in the liver. People taking fennel essential oil over a long period of time show a colour change in the liver tissue (Franchomme & Pénoël 2001 p. 105). Thujone, thymol and turpentine oil may damage the liver following oral ingestion in high doses (Schilcher 1985 p. 229). Liver toxicity seems to arise when innocuous essential oil components are metabolized to toxic chemicals, as with pulegone, found in many of the mint oils. Also to be treated with caution (based largely on animal testing using very high doses) are methyl chavicol (found in Artemisia dracunculus [tarragon]), safrole (in Sassafras albidum), myristicin and elemicin (in Myristica fragrans [nutmeg]) and apiole (in Petroselinum sativum (fruct.) [parsley seed]).
Some essential oils have an effect on the kidneys which is regarded as stimulating and beneficial in low doses, but which could be classed as toxic if the quantity of oil used is excessive or it is used for too long a time. Juniperus sabina [savin] is mentioned by Schilcher (1985 p. 229) as causing damage to the kidneys, even when applied externally. Large quantities of the ester methyl salicylate, found in the oils of Gaultheria procumbens [wintergreen] and Betula lenta [sweet birch], and of safrole (found in S. albidum [sassafras]) are nephrotoxic. Sandalwood and turpentine taken orally in excessive doses can also cause kidney damage (Tukioka 1927).
There are several essential oils which may have unwanted side effects during the first trimester of pregnancy, e.g. they may be emmenagogic and are therefore best avoided at this time, especially as, once in the body fluids, they may pass through the placenta. It is known that, although the placenta acts as a barrier against both neutral and positively charged molecules, those which are negatively charged can cross it fairly easily (Maickel & Snodgrass 1973); it is also known that small molecules with a molecular weight of less than 1000 are able to pass through the placenta (Baker 1960). Therefore, as many essential oil molecules are negatively charged and all have molecular weights of less than 250, it can be assumed that essential oils do pass through the placenta. Their effects on a newly formed fetus have not yet been studied.
Essential oils may, however, be used correctly and safely later in pregnancy, but the situation is not clear. ‘Crossing the placenta does not necessarily mean that there is a risk of toxicity to the foetus; this will depend on the toxicity and the plasma concentration of the compound’ (Tisserand & Balacs 1995).
Few authors are able to justify their recommendation of particular aromatherapy oils. This lack of firm information has led many aromatherapists to avoid using any allegedly unsafe oils during the whole gestation period, even though some of the proscribed oils are not necessarily unsafe in relation to pregnancy.
Many lists of oils to be avoided during pregnancy include those containing aldehydes and phenols (such as Cymbopogon citratus [lemongrass] and Syzygium aromaticum [clove bud], whose toxicity is mainly a potential irritant effect on the skin) and contraindications do not specifically relate to pregnancy (see Appendix B.6 on the CD-ROM). Some oils listed contain coumarins and are therefore photo sensitizers (Appendix B.7 on the CD-ROM), but again this does not affect their use with particular regard to pregnancy. The essential oils listed in Appendices B.6 and B.7 should be treated with caution by everyone, not just those who are pregnant. Balacs (1992) began the clarification of this area by giving reasons for his list of oils to be avoided in pregnancy. This article and The Aromatherapy Workbook (Price 2000 p. 131) are intended to be more informative and to put back into perspective the use of powerful and extremely useful essential oils during pregnancy. Another interesting point to consider is that a woman is often unaware of being pregnant at first – occasionally up to 4 weeks or more – and could be using essential oils regularly during that time. Where this is known to have happened, however, no ill effects have been reported.
To save confusion and misuse, members of the general public (and inadequately qualified aromatherapists) are best advised not to use an essential oil appearing on any restrictive list during pregnancy without having been given advice by a competent aromatherapist; there are a number of essential oils which can be safely used during this time.
A number of essential oils are labelled as toxic without any evidence of their causing harm to human beings, except by gross misuse. Toxicity of the main component of an essential oil does not always constitute proof that the whole essential oil is toxic to humans, whatever the results of research on rats and mice (which are injected with or made to ingest essential oils – see Part I of this chapter). The results of animal testing cannot be directly extrapolated to humans, and because of the small amounts used in aromatherapy massage the effects of the essential oils would be 100 000 times less hazardous than the amounts used in animal testing (Tisserand & Balacs 1991).
Empirical evidence accumulated over many years illustrates that when used in small doses (and for a restricted period), even the so-called toxic oils on the lists referred to do not normally present a hazard. Mentha pulegium [pennyroyal] is reputed to be a strong abortifacient and a much impugned oil so far as pregnancy is concerned. The following selection of the many cases of women who took large doses of pennyroyal deliberately are all recorded in medical journals.
• To induce menstruation, one woman took about 15 mL of pennyroyal and suffered acute gastritis, but recovered fully (Allen 1897).
• Another made herself an infusion with about 15 mL of pennyroyal and ‘threepennyworth of rum’. She felt sick after 10 minutes and later became unconscious; she vomited when roused shortly afterwards, but recovered by the next day (Braithwaite 1906).
• To induce abortion, a 22-year-old American woman took approximately 10 mL of pennyroyal and felt dizzy within an hour, recovering the same day. Tests showed her liver and renal functions to be normal and she was discharged 2 days after admission (Sullivan & Peterson 1979).
• A 24-year-old mother of two, taking an unknown amount of pennyroyal and cohosh herb in two separate doses (evening and the following morning), succeeded in aborting on the second day but was admitted to hospital seriously ill. Towards the end of 10 days her general condition was recorded as being satisfactory – all damaged tissues seemed to have recovered fully, except the kidneys. However, she developed pneumonia and died 3 days later (Vallance 1955). [In this case it is not clear whether the abortion was due to pennyroyal or cohosh, or a combination.]
• An 18-year-old American girl took about 30 mL of pennyroyal, thinking she was pregnant. After severe vomiting and vaginal bleeding, she suffered a cardiopulmonary arrest 4 days after ingestion. She died 2 days later following a second cardiopulmonary arrest (Sullivan & Peterson 1979).
Mentha pulegium can contain varying amounts of the ketone pulegone (see Potential toxicity, below) depending on the country of origin and whether cultivated or wild. Lawrence (1989) quotes the pulegone content found in M. pulegium from the following countries: Uruguay (1985): 26.8%, Angola (1976): 42%, Greece (1972): 61.9%, Chile (1986): 92.6%.
The average content in the essential oil is normally around 65%, but it is not known what percentage of pulegone was in the oil / herb /infusion used by the women quoted above. It is difficult therefore to be certain about what dosage level is safe and when the amount poses a danger. What is quite clear is that swallowing large quantities (15–25 mL) of any essential oil, even one considered to be safe, constitutes gross misuse and may cause significant unwanted side effects (see Part I of this chapter). Herbal medicines are promoted as more ‘natural’ and safer than conventional over-the-counter medicines (Huxtable 1992), but herbal preparations are not subject to the same scrutiny and certification; pennyroyal is one widely available herbal medicine that can be life- threatening after ingestion.
Emmenagogic essential oils are recommended to promote menstrual flow in non-pregnant women suffering from amenorrhoea, or irregular or scanty menstruation. The oils listed below are considered by the majority of writers to be emmenagogic. Such oils should not be used in the first trimester of pregnancy, unless needed in an emergency or for a short period of time. Where there is a history of miscarriage, they should not be used at all.
• Achillea millefolium [yarrow] contains little or no thujone, as opposed to sage oil, which may contain 50% (Leung & Foster 1996 p. 458), but the plant has been used as an abortifacient in the past (Chandler, Hooper & Harvey 1982) and so the essential oil must be regarded as emmenagogic until proved otherwise. There is also a taxonomic problem with yarrow: Lawrence (1984) speaks of yarrow being a complex of hardly separable species, which is another reason for caution.
• Foeniculum vulgare var. dulce – also hormone-like, diuretic and galactagogic; facilitates delivery (average phenolic ether content 60%).
• Myristica fragrans [nutmeg] – also facilitates delivery; is hallucinogenic in overdose (average phenolic ether content 6%).
• Pimpinella anisum [aniseed] – also hormone-like; facilitates delivery (average phenolic ether content 83%).
• Salvia officinalis – also hormone-like; prepares the uterus for labour (average ketone content 35%).
The following essential oils are those that some suggest are emmenagogic and should be used with caution during pregnancy. No evidence has yet been produced to support or refute these suggestions, and under the guidance of a competent aromatherapist it would appear that their use may not be detrimental to the wellbeing of a pregnant woman. However, this does not necessarily mean that all of them should automatically be regarded as safe, because even safe oils can be used wrongly and unsafely.
• Chamaemelum nobile [Roman chamomile] (contains around 13% of a ketone). Indicated for menstrual problems (dysmenorrhoea, amenorrhoea) linked to nervous troubles Valnet 1980 pp. 104–105).
• Matricaria recutita [German chamomile] – hormone-like (Franchomme & Pénoël 2001 p. 396) (contains around 30% oxides).
The above two essential oils are recommended for amenorrhoea, but their emmenagogic properties are generally considered to be very mild.
• Commiphora myrrha, C. molmol [myrrh]. Myrrh is thought to be an emmenagogue, perhaps because it is hormonal; in Grieve (1991 p. 572) it is not made clear whether the plant or the essential oil is responsible for the therapeutic action (see Levisticum officinale below). As a result, it appears in many British aromatherapy books as a proven emmenagogue. None of the French books cite it as such, and Balacs (1992) considers it to have ‘doubtful toxicity’.
• Juniperus communis (fruct. ram. fol.) [juniper berry, twig, leaf] – diuretic. Formacek and Kubeczka (1982) found J. communis to contain approximately 87% terpenes, with a small percentage of alcohols and no ketones, yet a J. communis cited by Franchomme and Pénoël (2001 p. 389) is given as containing ketones (percentages not given). Valnet (1980) gives it as an emmenagogue, though he does not mention amenorrhoea as an indication – only painful menstruation, and it is not clear whether he means the essential oil or a decoction of the berries; this is crucial, as larger plant molecules can have different effects from the smaller volatile molecules. Franchomme makes no reference whatsoever to the reproductive system, nor do four other French aromatherapy books. The property of J. communis fruct. [juniper berry] upon which all are agreed is its diuretic effect.
• Levisticum officinale [lovage] – diuretic (contains around 50% phthalides, about which not much is known). The essential oil is distilled from the roots. The leaves were once used as an emmenagogue (Grieve 1991 p. 500), which may be the reason why the essential oil has been assumed to be emmenagogic also.
• Melaleuca cajuputi [cajuput] – hormone-like (contains around 30–40% oxides). Franchomme (Franchomme & Pénoël 2001 p. 397) is the only person to advocate prudent use of this essential oil during pregnancy; it is not given as emmenagogic.
• Mentha x piperita [peppermint] – hormone-like (contains 20–50% alcohols, 15–40% ketones). Like several essential oils, the main constituents in peppermint essential oil are variable, making decisions regarding its emmenagogic properties difficult. The pulegone content is usually 0.3–0.6%, though that of American peppermint may be just under 3% (Gilly, Garnero & Racine 1986). Peppermint is sometimes distilled after drying the plant, when the ratio of menthone (16–36.1%) to menthol (46.2–30.8%) is radically different (Fehr & Stenzhorn 1979). Valnet (1980 p. 173) lists it as an emmenagogue, though Franchomme & Pénoël (2001 p. 401–402) list it as a hormone-like oil which regulates the ovaries; they do not contraindicate it for pregnant women. Bardeau (1976 p. 216) states that it calms painful periods.
• Ocimum basilicum [European basil]. Because of its phenolic ether content (methyl chavicol), which varies within wide limits depending on the species, the origin and the time of harvesting, basil is often cited as an emmenagogue. Valnet (1980) cites it as such, although Franchomme & Pénoël (2001 p. 408) give no mention of its use for any gynaecological condition and state that regardless of the percentage of methyl chavicol, there are no known contraindications. Most of the basil oils available to aromatherapists contain a high percentage of methyl chavicol, the lowest being around 50% (and often as high as 75–80%).
• Origanum majorana [sweet marjoram] (contains around 40% terpenes and 50% alcohols). When this essential oil is contraindicated for pregnancy it is no doubt being confused, owing to the use of the common name, with Thymus mastichina [Spanish marjoram]. The latter essential oil is a species of thyme and has totally different constituents, with an oxide content of 55–75%. There is no mention in any of the French aromatherapy literature of any emmenagogic effect or of having to treat O. majorana with caution, and no evidence has yet been produced to support the contraindication of T. mastichina, despite its high oxide content. Until there is, it may be prudent to use this latter oil with care. ‘Marjoram’ essential oil should not be purchased without knowing its botanical name.
• Rosa damascena, R. centifolia [rose otto] – hormone-like (contains over 60% alcohols). Rose otto is cited several times as being antihaemorrhagic (Bardeau 1976 p. 268, Franchomme & Pénoël 2001 p. 421, Roulier 1990 p. 298), but no sources mention its having any emmenagogic properties. Wabner (1992 personal communication) states that it regulates menstruation because of its hormonal influence, but that it is not emmenagogic.
• Rosmarinus officinalis [rosemary] – different chemotypes (ketone content 14–35%, oxide content 18–40%). The chemotype labelled by Franchomme (Franchomme & Pénoël 2001 p. 421) as an emmenagogue is the camphoraceous rosemary. He cites the verbenone chemotype as neurotoxic and abortive (which would indicate care when used with pregnant women), but gives no contraindications regarding the reproductive system for the cineole chemotype. Roulier (1990 p. 298), on the other hand, gives no contraindications regarding the verbenone chemotype, yet warns against use of both the cineole and the camphoraceous type on pregnant women. He gives neither of them as an emmenagogue. The rosemary quoted in Valnet (1980 p. 177), which is not given as a specific chemotype and does not appear to contain verbenone, is given as an emmenagogue.
• Salvia sclarea [clary] – hormone-like (contains 60–70% esters). Clary is cited only for its hormonal properties (Roulier 1990 p. 302) specifically in regard to amenorrhoea, but with no mention of it being emmenagogic. It is considered emmenagogic by Holmes (1993), although no authority is given. According to Culpeper (1983), the juice of the herb (not the essential oil), drunk in beer, accelerates menstruation. This could be due to its hormonal properties, as sclareol (the diterpenol responsible for the hormone-like property of clary) is present in the juice in a much higher quantity than in the essential oil, owing to its molecular weight (see Ch. 1).
• Vetiveria zizanioides [vetiver] (average ketone content 22%). Only one source (Franchomme & Pénoël (2001 p. 433) has been found to cite this oil as an emmenagogue.
The purpose of training is to ensure minimum risk and maximum benefit to clients; unfortunately, some training programmes instil fear and insecurity through insufficient, inadequate and often incorrect teaching. Aromatherapy schools and colleges should adopt a sensible approach to the subject of toxicity and not – as many do, perhaps owing to inadequate education of the teachers – sensationalize and exaggerate the possible harmful effects of essential oils. It is up to aromatherapists to have an inquiring mind and make sure that the toxicity information they have been taught is constructive to their work, not destructive. This is not to say that essential oils, even if carefully chosen, can be used carelessly: relevant knowledge and care in use are required.
Aromatherapy in the UK developed from a beauty therapy aspect, where a gentle approach was combined with a high dilution unlikely to have any risk in use. Teaching avoided – and still does – the topics of intensive or internal use, where potential hazards need careful consideration. Today essential oils are rarely used undiluted, but in such high dilution (usually 1–4%) that the only precaution necessary is to be aware of contraindications in circumstances such as epilepsy, pregnancy, skin sensitivity etc. With comprehensive knowledge, applied prudently, these advanced uses are equally as safe as any other method.
The concentration of the oils to be used and duration of treatment depend on the correct assessment of the client’s state of health. To attack an infection, a strong dose of a powerful – and possibly so-called ‘toxic’ oil – is required for a short period; for a chronic problem such as asthma, a much smaller dose of ‘safe’ oils is effective and can be used for a longer time. These choices can be made only if the therapist has sufficient knowledge of the properties and chemistry of an essential oil and the common sense to know whether or not a ‘toxic’ oil could be used successfully on a particular client to give beneficial results.
• Keep out of the reach of children.
• Essential oils are not to be ingested without specific professional advice.
• Never remove a dropper insert from a bottle of essential oils in order to prevent accidental ingestion; if this should happen, then medical assistance must be sought immediately.
• Do not apply neat to the skin unless under the direction of a suitably qualified therapist.
• Idiosyncratic reactions to essential oils are possible; immediate medical assistance must be sought.
• Neat essential oils can be removed from the hands by washing thoroughly with a mild detergent to prevent transference to other parts of the body (e.g. the eyes).
• If essential oil does get into the eye, the eye should be flushed with a good-quality carrier oil, which will dissolve the oil (water does not).
• See also Appendix C on the CD-ROM.
The need for a dispassionate and scientific attitude towards the possible dangers of essential oils has been demonstrated, as has the need for skill in their selection and prescription. Various potentially hazardous situations have been identified, but no harm should occur if the guidelines for safe administration are followed. Despite this, essential oils must be treated as hazardous substances (see Appendix C on the CD-ROM). In order to comply with regulatory requirements, an assessment of the potential risks associated with their use must be carried out in order to prevent anyone who may come into contact with them from being harmed.
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