Claims for therapeutic benefits of essential oils are often bogus
Too much false information was disseminated regarding the therapeutic benefits
of essential oils, Dr Maria Lis-Balchin (London, United Kingdom) told the symposium.
In some cases there was confusion over names, and claims were made based on
the traditional uses of a different plant. This was especially the case for
the oil of Pelargonium species. These oils were commonly known as geranium oils
and their reputed effects were based on the traditional uses, often of water
or alcohol extracts, of Geranium species, which did not produce much oil but
had high levels of tannins.
Sometimes stated claims were based on clinical trials, but closer examination
of many of these trials revealed that they were of poor quality. Some of the
better trials had shown little difference in effect. And some, notably a recent
one on the use of essential oils in eczema, had shown that the condition worsened
in the group treated with the oil.
Dr Lis-Balchin emphasised that evidence from in vitro tests was useful and indicated
that essential oils displayed some interesting activities, but care had to be
made into translating results into in vivo or clinical situations. She quoted
her own work which had shown antioxidant effects in thyme oil in vitro and then,
when applied to mice, had increased the levels of polyunsaturated fatty acids,
thus suggesting an in vivo effect.
In an address which concentrated on the reputed activity of oils used in aromatherapy
in the light of scientific evidence, Dr Lis-Balchin pointed out that because
oils were used in diffusers, which vapourised them into the general atmosphere,
most of the dosage received was by inhalation, and the dose was likely to be
very small. Direct inhalation of the oil from an impregnated cloth would achieve
a higher dose but the most common method of application was from massage, using
a dilution of the essential oil in a fixed oil such as almond oil. In these
cases the dose would be small.
More work was still needed to determine how much oil was absorbed systemically.
This could be important for some oils that were used for treating topical conditions
such as athlete’s foot (eg, tea tree oil) or as counter-irritants for relief
of muscle pain (eg, turpentine oil).