Aromatherapy Research Article
January 2015
Uplifting Essential Oils
I hope you had a wonderful Christmas and New Year’s Eve! Now that the festive season
is over and New Year’s Eve celebrations have come and gone, I’m sure I’m not the only
feeling a bit run and tired down from over-indulging in food and drink! In this month’s
article we will be exploring scientific research into essential oil that may have uplifting
properties, to help combat post-holiday blues and uplift and refresh for the New Year
ahead. We will also be exploring research behind immunostimulants which could
possibly aid in preventing illnesses taking hold when you’re feeling run down or even
decreasing the duration of an illness.
Uplifting Essential Oils
There is a plethora of essential oils that are reportedly uplifting. Uplifting properties of
oils could be investigated scientifically by looking at properties such as antidepressant
effects (which may combat depression), anxiolytic and/or sedative effects (which could
reduce nervous tension and restlessness) and central nervous system stimulants (which
increase energy levels, concentration and motivation). Below is a selection of just some
of the oils that could be useful.
Bergamot
Bergamot (Citrus bergamia) is traditionally used as a folk medicine in its native Italy for
fever and parasitic worms, however, more recently bergamot has been recommended in
aromatherapy for the treatment of stress induced anxiety and depression (Lawless,
1997). Limonene constitutes 26.7-42.5% of bergamot. It has been shown to exert
anxiolytic effects in rats (De Almeida Costa et al., 2012), and was found to significantly
increase the levels of the neurotransmitters such as GABA and serotonin, which are
involved in mood and anxiety, in mouse studies, (Chen et al., 2012). Furthermore,
linalool constitutes 11% of bergamot oil (Price and Price, 2011), which may contribute
to its anxiolytic effect. In a study of rats, bergamot oil was found to exert a stimulant
effect on both brain activity, as measured by EEG, and behaviour, as measured by
increases in exploratory behaviour (Bagetta et al., 2010). This suggests that bergamot
could be a good oil to uplift the mood by reducing anxiety and depression and aid in
restoring motivation and concentration by exerting a central nervous system stimulant
effect.
Lemon
A human clinical trial conducted by Knaso (1992) found that subjects rated their mood
as more pleasant when a room was scented with lemon essential oil than with a
malodourous or unscented room. The lemon odour also appeared to influence their
personality ratings, as when exposed to the lemon odour, participants believed more in
an internal source of control and the less they believed that their lives were controlled
by chance or others than when exposed to malodour or no odour. They were also
significantly less likely to report symptoms of existing health problems when exposed to
lemon odour (Knasko, 1992). This suggests lemon can uplift the mood in humans, in
support of its use in aromatherapy. Limonene constitutes 55-80% of lemon oil (Price
and Price, 2011), and citral, which has been shown in animal studies to exert
antidepressant effect (Komori et al., 1995). These components could therefore be partly
responsible for improve the subjects’ moods.
Ylang Ylang
In Indionesian culture, ylang ylang flowers are scattered or extract sprayed onto the
beds of newlyweds (Rhind, 2012) as it is reportedly relaxing, anxiolytic and euphoric,
thus considered an aphrodisiac. These effects have been investigated in small-scale
human clinical trials, using both topical application (Hongratanaworakit and
Buchbauer, 2006) and inhalation (Moss et al., 2008). To assess the outcome of the use of
ylang ylang on mood, visual analogue scales were used, where the participant marks
their mood on a scale of two extremes e.g. relaxed/anxious. Both studies found ylang
ylang to significantly increase calmness and relaxation compared to controls (no
essential oil). Hongratanaworakit and Buchbauer (2004; 2006) also found a significant
decrease in heart rate and blood pressure with topical application and inhalation of
ylang ylang aroma, supporting the relaxing properties of the oil. However, inhalation of
ylang ylang significantly increased feelings of alertness and attentiveness, suggesting
that this oil is not a sedative, but more of a ‘harmonising’ oil (Hongratanaworakit and
Buchbauer, 2004).
Palmarosa
Palmarosa oil could be useful in lifting feelings of depression, due to the results of a
study indicating that an ethanolic extract competitively inhibited monoamine oxidase
activity in an rat brain mitochondrial monoamine oxidase in vitro preparation (Gacche
et al., 2011). Monoamine oxidase is responsible for removing serotonin, dopamine and
other neurotransmitters that play a role in mood from neuronal synapses, thus
inhibiting monoamine oxidase would increase the amount of available
neurotransmitter. Monoamine oxidase inhibitors are commonly used drugs for mood
disorders such as depression and anxiety. If palmarosa does inhibit monoamine oxidase
activity in the brain upon inhalation, this may be useful for lifting the mood in
depressive states and relieving anxiety.
Frankincense
Frankincense has been highly valued for centuries as a tool for meditation. Using
behavioural models, it was found that incensole acetate, a compound found in the resin,
exerted anxiolytic and anti-depressive effects. These findings were corroborated by
immunohistochemical mapping of mice brains following incensole acetate
administration. Incensole acetate was assessed for its behavioural effects on mice with
the gene missing for an ion channel called TRPV3, which is thought to be connected to
mood states. No anti-depressive and anxiolytic effects were seen in mice missing the
TRPV3 gene, suggesting that incensole acetate exerts anti-depressive and anxiolytic
effects via TRPV3 channels. This is a distinct pathway compared to anxiolytic and
antidepressant drugs currently in use (Moussaieff and Mechoulam, 2009). The possible
anxiolytic and antidepressant properties may therefore aid in calming and lifting the
mood.
Cypress
A mouse study of cypress essential oil found it to possess central nervous system
stimulant effects, as it decreased conditioned avoidance response rates to electric
shocks upon administration of cypress oil (Umezu, 2012). A further mouse study found
cypress essential oil to significantly reduce immobility of mice in a swimming test
(immobility is a behavioural instinct with forced swimming), with the same result being
achieved with caffeine, also suggesting cypress has a stimulating effect on the central
nervous system (Lim et al., 2005). Furthermore, it has been noted that cypress could
improve cognition and memory (Dobetsberger and Buchbauer, 2011).
Jasmine
Jasmine absolute was found to act as a central nervous system and behavioural
stimulant when administered topically to the skin of the stomach of 40 healthy
participants. This was concluded due to a significant increase in autonomic parameters
of blood pressure, pulse rate, blood oxygen saturation, breathing rate and significantly
increased feelings of attentiveness and energy than subjects in the control group
(Hongratanaworakit, 2010).
Sweet Orange
Hongratanaworakit et al. (2003) found that through inhalation of sweet orange aroma
(olfactory stimulation) by humans, heart rate and subjective ratings of alertness
significantly increased, suggesting sweet orange has a stimulating activity.
Roman Chamomile
Roman Chamomile has a long history of medicinal use, and is commonly employed for
treating nausea and inflammation. Chamomile is also often used as a relaxant to calm
frayed nerves, such as in a massage or consumed in a tea. This use is supported by a
study finding that massages of Roman Chamomile for 20 minutes, 3 times a week
significantly improved self-esteem and decreased anxiety of cancer patients (Srivastava,
Shankar and Gupta, 2010). A mouse study reported finding that roman chamomile
significantly increased shuttle type avoidance responses, a behaviour indicative of
central nervous stimulation, suggesting roman chamomile is a central nervous system
stimulant (Umezu, 2012).
Black Pepper
Inhalation of black pepper essential oil for 7 minutes was found to enhance adrenaline
concentrations 1.7-fold and increase systolic blood pressure compared to inhalation of
an odourless solvent, in a small study of healthy women (Haze, Sakai and Gozu, 2002).
An increase in adrenaline and sympathetic nervous system activity serves to stimulate
the body for action, by increasing blood flow to skeletal muscle and mobilise energy
stores, bronchodilation to increase oxygen intake and pupil dilation for better vision.
Basil was very highly regarded in the past, and even regarded as a ‘King among plants’
(Davis, 1990). It was thought to clear the mind, for instance, some Indian tribes chewed
basil leaves for inspiration. It is also reportedly a stimulant (Sellar, 1992).
Intraperitoneal injection of basil essential oil has been found to significantly increase
the ambulatory activity of mice. Ambulatory activity is a type of spontaneous central
nervous system activity, which increases with central nervous system stimulation. Thus
basil may exhibit CNS stimulant effects (Umezu, 2013)
Peppermint
Peppermint essential oil is reportedly a central nervous system stimulant, which is
supported by animal studies showing an increase in activity of mice upon inhalation of
peppermint essential oil as opposed to no odour (Dobetsberger and Buchbauer, 2011).
Peppermint’s central nervous system stimulating effect on humans was also
investigated in a study of 44 healthy volunteers. A concealed essential oil diffuser was
used to deliver the essential oil via inhalation, and several cognitive parameters were
measured in comparison to a control of no aroma. Significant increases in alertness
reported by volunteers using a mood scale were found compared to controls, as well as
a significant increase in memory function (Moss et al., 2008). A small trial also reported
that peppermint odour acted as a CNS stimulant; significantly increasing alertness,
motivation and performance and decrease fatigue and frustration in a simulated driving
test (Raudenbush et al., 2009).
Cinnamon
Raudenbush et al. (2009) also studied the effects of cinnamon odour on alertness,
motivation and performance and decreased fatigue and frustration in a simulated
driving test, and found that cinnamon odour did indeed significantly improve these
parameters. A small human study reported that cinnamon odour acted as a CNS
stimulant; significantly increasing alertness, motivation and performance and decrease
fatigue and frustration in a simulated driving test (Raudenbush et al., 2009).
Immunostimulant Oils
Feeling run down? Some essential oils have been found to stimulate branches of the
immune system, so could possibly help keep up your defences from illnesses that might
take hold with a low immune function.
Echinacea
Echinacea is the most popular herbal immune stimulant in North America and Europe
(Oomah et al., 2006). The effect of Echinacea on the immune system has been studied
extensively both in vitro and in vivo, with an overall consensus that Echinacea extracts
act as immune stimulants, but tends to be referred to as immunomodulatory, as
widespread immune stimulation can be harmful (Barrett, 2003).
Echinacea has been investigated in both in vitro and in vivo against macrophages, a type
of white blood cell involved in the immediate immune response to infection and injury
by engulfing debris such as microbes, and recruit other cells by producing proinflammatory cytokines. It was found that both mouse and human macrophages had
greater phagocytic (engulfing) activity and increased their production of the cytokines
IL-1,IL-10 and TNF-α when treated with Echinacea compared to controls (Barnes et al.,
2005). Furthermore, samples of peripheral white blood cells from healthy humans, AIDS
patients and ME patients (who both have depressed immune systems) treated with
Echinacea revealed an increase in natural killer cell function. This is supported by a
mouse study performed in vivo in normal, leukemic and aging mice (who have
depressed immune systems), which also found an increase in natural killer cell function
(Barnes et al., 2005). As the name suggests, natural killer cells are important in immune
responses as they are primed to kill immediately and don’t need activation by other
cells. They specialise in killing virally-infected cells, preventing spread to the
surrounding tissues. This is therefore a potential mechanism of Echinacea’s reported
use in viral infections.
When Echinacea root was administered to humans orally in an ethanol extract for 5
days in a double-blind placebo-controlled trial, phagocytic activity was increased in
peripheral blood neutrophils, suggesting Echinacea’s immunostimulant effects can be
seen in humans. However, these results were not found when using acid-resistant
capsules of Echinacea root, ethanol extract of Echinacea herb and root prepared for oral
ingestion, and Echinacea in a complex preparation for injection, suggesting that the root
of administration is important and should be investigated further to find the best way to
increase immune function with Echinacea. Seven double-blind, randomized clinical
trials were conducted in Germany between 1984 and 1997, with a total of 910 subjects.
Two studies looked at the appearance of flu-like symptoms, and five studies looked at
the appearance of upper respiratory tract symptoms, as determined by self-reporting
and physical examination. All seven studies showed a significant benefit due to taking
Echinacea, supporting the use of Echinacea to modify the severity and duration of cold
symptoms (Percival, 2000).
Frankincense
Frankincense is classically considered to be an immunostimulant. While little research
has been performed to determine if this is the case, one study looked at whether it could
induce proliferation of T-lymphocytes. T-lymphocytes were isolated from peripheral
human venous blood and treated with 10% frankincense oil solution in vitro, or positive
controls of Echinacea and levamisole and negative controls of the immunosuppressants
cyclophosphamide and cyclosporine. Frankincense was found to induce 90%
lymphocyte proliferation, which is comparable to the positive controls of Echinacea and
levamisole (Mikhaiel et al., 2003). This supports the traditional uses of frankincense as
an immunostimulant. In a further study, the authors looked at different compounds
within frankincense resin to try to determine which was responsible for the
immunostimulant effect. The degree of the proliferative response could not be
replicated with individual compounds in frankincense, suggesting they work in synergy
to stimulate the immune system. However, the authors of the study did not differentiate
between the response of different types of T-lymphocytes, which respond to either
bacterial or viral infection, so it is hard to know whether this immune response would
be useful for fending off colds and flu if this immunostimulant effect translated to in vivo
conditions.
Clove
Carrasco et al. (2010) investigated the effects of oral administration of clove, ginger and
sage oils upon the white blood cells of healthy and immunosuppressed mice. It was
found that after seven days, the total white blood cell count of both non- and
immunosuppressed mice had increased in a dose dependent manner. For example,
200mg/kg of clove oil increased the white blood cell count in non-immunosuppressed
mice by an average of 71.1% in seven days. Ginger and sage oils did not have a
significant effect on total white blood cell count. Clove essential oil was found to
stimulate a cell-mediated response as it caused an increase in delayed-type
hypersensitivity reactions. Cell-mediated responses are important for defending against
viruses and intracellular bacteria and fungi, suggesting clove could help activate this
response to protect against these, however further research into the mechanisms
behind this response and trials in humans are needed to confirm if it would be a useful
immunostimulant.
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