Scientific proof of EO efficacy aroma science Known bioactivities of EOs

These include: antimicrobial effects, effects on the CNS, pharmacological effects and various other miscellaneous effects.

Antimicrobial activity

EOs have been used externally to eradicate fungal or bacterial infections since the Black Death (and before); doctors would wrap scarves soaked in EOs like camphor round their necks and over their mouths when visiting patients (Valnet, 1982). This did not prevent the death per se, as the doctors rarely went near the patients, and only poked them with a long stick from a distance, to ascertain whether they were alive or dead. In the Second World War, wounded soldiers had their wounds treated with EOs until penicillin and other antibiotics became available (Valnet, 1982). Many EOs have considerable antimicrobial activity (Maruzella and Henry, 1958; Maruzella and Sicurella, 1960; Youzef and Tawil, 1980; Moleyar and Narasimham, 1987; Lis-Balchin and Deans, 1997; Lis-Balchin et al, 1998). Plant EOs like thyme and oregano, are extremely potent antimicrobials in vitro and can have a considerable effect on a wide range of different bacteria (Lis-Balchin, 1995; Lis-Balchin et al, 1998). Lavender is not strongly antimicrobial by comparison, and there is a substantial difference between the bioactivity in different lavender oils from different sources (French lavender, spike lavender etc.) and also the same oil from a different supplier (Lis-Balchin et al., 1998).

The antimicrobial activity of some of the EOs is often regarded by aromatherapists as proof of the aromatherapeutic usage. However, the actual mode of application of such EOs is far removed from the proper definition of aromatherapy, which is treatment with odours.

Effect on CNS

(1) Effect on mood — Many fragrances have been shown to have an effect on mood and in general, pleasant odours generate happy memories, more positive feelings and a general sense of well-being (Warren and Warrenburg, 1993). Much of this type of research has been conducted by perfumery companies to boost sales (Jellinek, 1956) and some EOs have also been applied in hospitals in the United States to create a more happy and positive atmosphere and also in offices and factories in Japan to enhance productivity. Even in the times of Culpeper (1653), lavender was stated to have effects on the minds as well as the body: there is, however, some discrepancy about the species involved, as spike lavender was used medicinally and the L. angustifolia was used in perfumery, but could also have been used as a the mind-bending agent!

(2) Psychological and physiological effects — Many essential oil (EO) vapours have been shown to depress Contingent Negative Variation (CNV) brain waves in human volunteers (Table 16.2) and these EOs are considered to be sedative. Others increase CNV and are considered stimulant. The effects of inhaling different EOs on the CNV can be compared to the effect on mouse motility and the direct effect of the EO on smooth muscle in vitro (Table 16.2). Although there is a great difference in the application of the oils and the measurement of their effect, there is surprisingly, a frequent agreement. Lavender (of unspecified genus) was found to have a sedative effect on man (judging by CNV studies) (Kubota et al., 1992; Torii et al., 1988; Manley, 1993) and also had a 'positive' effect on mood, EEG patterns and Math computations (Diego et al., 1998) and also caused reduced motility in mice (Buchbauer, 1991; 1993; Jager et al., 1992; Kover et al., 1987; Ammon, 1989). However, Karamat et al. (1992) found that lavender had a stimulant effect on decision times in human experiments. The effect of three different 'lavenders' on the smooth muscle of the guinea-pig in vitro (Lis-Balchin et al, 1997c) showed mainly a sedative effect, but the true L. angustifolia, be it a commercial EO, always gave an initial contraction followed by a relaxation. There was also a good agreement between the effect of individual EOs (and mixes of three or more) on smooth muscle in vitro and the predicted effect on clients, as judged by aromatherapists (Lis-Balchin and Hart, 1997a).

Table 16.2 Sedative and stimulant EOs

EO

Sedative

Stimulant

Lavender

1, 2, 4, 5, 8, 11

5, 6

Jasmine

5

1, 2, 4, 9

Peppermint

5

1,2, 3,9

Rose

5, 7

2, 3

Rosemary

1, 4, 5

8, 11

Sandalwood

1, 2, 3, 4, 5

Valerian

1, 3, 5

3 Manley (1993): CNV studies in man.

4 Buchbauer (1991; 1993); Jager et al. (1992): motility of mice.

5 Lis-Balchin (1995); Lis-Balchin et al. (1996): smooth muscle in vitro.

6 Karamat et al. (1992) decision times.

7 Kikuchi et al. (1991) heart rate in man.

9 Ludvigson and Rottman (1989) in man.

Sources

3 Manley (1993): CNV studies in man.

4 Buchbauer (1991; 1993); Jager et al. (1992): motility of mice.

5 Lis-Balchin (1995); Lis-Balchin et al. (1996): smooth muscle in vitro.

6 Karamat et al. (1992) decision times.

7 Kikuchi et al. (1991) heart rate in man.

9 Ludvigson and Rottman (1989) in man.

Long and Roberts (1990) showed that at low concentrations, the expectancy of the odour produced changes in CNV rather than the odour itself. Eighteen subjects were presented with equal intensities of jasmine, lavender and galbanum in high concentration, and three mixes which were labelled low levels of jasmine, galbanum or lavender but were in fact all the same. The CNV effects were studied against no odour. The CNV changes for lavender were lowest, followed by galbanum and jasmine: the three mixtures produced the same results, that is, for the expected odours rather than for the same mixture in each case. The subjects assessed the primary odours according to intensity and pleasantness, but few correlations between these and CNV changes were found. Most subjects hated lavender.

King (1988) studied anxiety-reducing effects of fragrances using electromyography. The effect of ambient odour compared to no odour in sessions one week apart on creativity, mood and perceived health was studied in fifteen men and fifteen women (Knasko, 1992). The odours varied: lemon, lavender and dimethyl sulfide (DMS, an unpleasant odour). With lemon, fewer health symptoms were reported compared with the non-odour day. Subjects in the DMS group were less happy than those in the lavender group on both odour and non-odour days. The order of giving the odours affected the outcome, which was not very helpful in the study. However, there were no differences in arousal or creativity.

Inhalation studies in a group of forty staff and students, of rosemary oil versus lavender oil using EEG and simple maths computations, showed that lavender increased jS-power, suggesting drowsiness and the subjects stated that they were more relaxed, while rosemary instigated decreased frontal a- and j-power, suggesting increased alertness, and the subjects were faster and more accurate in the maths Diego et al. (1998). These results seem to show that odour has an effect on performance per se, but Knasko et al. (1990) used no odour, but lied to their subjects that odour would be given: they also got an improvement in carrying out tasks, that is, mind over matter!

An interesting single study involving an anosmic showed that, as in eight neurologically normal people, there were changes in cerebral blood flow (CBF) on inhaling 1,8-cineole, thus showing a positive brain effect to the oil despite the inability to smell it (Nasel et al, 1994). The results showed that in each case there was a global increase in CBF, without preference for a specific area.

There is some evidence that certain EOs can lower blood pressure, if it is elevated, for example, nutmeg (Warren and Warrenburg, 1993), but this has not been investigated with lavender oil.

Lack of evidence for direct action on tissues following skin absorption

There is virtually no scientific evidence, as yet, regarding the direct action of EOs, applied through massaging of the skin, on specific internal organs. This is despite some evidence that certain EO components can be absorbed (Table 16.3) when massaged into the skin or by inhalation and that some have a beneficial effect on ureteric stones when taken orally (Engelstein et al., 1992). Jager et al. (1992) showed that linalool and linalyl acetate was detectable in the blood after massage with lavender oil; the lavender oil could have been inhaled and not absorbed through the skin entirely. Buchbauer et al. (1992) found benzyl alcohol, benzaldehyde and 2-phenylethanol I the blood after inhalation of limeblossom and passiflora as well as the components themselves. Kovar et al. (1987) showed the presence of 1,8-cineole in the blood after rosemary oil was inhaled or given orally. Buchbauer et al. (1993b) also showed the presence of benzaldehyde and carvone in the brain after inhalation of the two components individually.

Table 16.3 Evidence for transfer of components of EO into blood/brain when applied to skin, orally or by inhalation

Source

EO administered

Components found in blood/brain

Jager et al. (1992)

Lavender (massage)

Linalool, linalyl acetate (blood)

Buchbauer et al. (1992)

Limeblossom and

benzyl alcohol,

Benzyl alcohol,

benzaldehyde

benzaldehyde,

passiflora and

2-phenylethanol

2-phenylethanol

(blood)

(inhalation)

Kovar et al. (1987)

Rosemary (oral and

1,8-cineole

inhalation)

(blood)

Buchbauer et al. (1993b)

Benzaldehyde,

Benzaldehyde,

carvone

carvone

(inhalation)

(brain)

Fuchs et al. (1997)

Carvone

Carvone

(massage)

(blood)

Furthermore, although many EOs are very active on many different animal tissues in vitro (Lis-Balchin and Hart, 1997a), we have no idea as yet whether their activity in minute amounts (as used in aromatherapy massage) can benefit the patient through direct action on target organs or tissues (Vickers, 1996) rather than through the odour pathway leading into the mid-brain's 'Limbic System' and thence through the normal sympathetic and parasympathetic pathways. There is also no proof that synergism occurs when mixtures of EOs are used (Lis-Balchin et al, 1997d).

EOs are used by some doctors in France and Germany as orally or rectally-introduced medicines; these involve large doses, sometimes in excess of 45 ml per day (Franchomme and Penoel, 1990) rather than the almost homeopathic doses used by aromatherapists in their massage oil mixes in the United Kingdom and the United States, which rarely exceed 0.5 ml per massage. Most of the EOs are of course volatalized during the massage.

Miscellaneous effects of EOs

Many plant EOs have been shown to have an antioxidant effect and this property has also been shown to effect the lipoprotein membrane composition of the cell walls, giving a reversal of the ageing profile of saturated fatty acids compared to the unsaturated fatty acid composition in young animals (Dorman et al., 1995). This has raised the banner of the benefits of EOs on longevity and youthful appearance of the skin. Unfortunately, lavender is not an antioxidant EO!

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