What is it?
Aromatherapy involves the use of plant extracts with distinct and pleasant odours. The extracts used are known as essential oils in the sense that they contain the “essence” of the plant, ie its characteristic fragrance. It is important for aromatherapists that these essential oils are extracted from plants, as they do not consider artificial compounds to have the same effects. However, studies show that the majority of people are not able to differentiate between the smell of essential oils and those of synthetic fragrances.
The use of substances based on their pleasant smell has been common since antiquity, with well-known examples from ancient Egypt and China. But the modern concept of aromatherapy – using essential oils with healing purposes – started in France in the 1920s with French chemist René-Maurice Gattefossé. Most aromatherapists do not claim to cure disease with essential oils, but rather to improve general wellbeing, particularly in terms of reducing stress and anxiety.
Aromatherapy can be administered by direct inhalation of essential oils (such as with a vaporiser), by indirect inhalation via a diffuser or oil lamp, or by application on the body in the form of massage with essential oils. Some aromatherapists consider that only inhalation of essential oils is aromatherapy, while all other applications count as phytotherapy (the use of plants or their components).
Is it safe?
The majority of aromatherapy clinical trials do not provide information on adverse effects experienced by participants. However, a systematic review found 71 reported cases of adverse effects related to aromatherapy use. The most common was dermatitis, a type of skin allergy, and although most of these patients made a full recovery, six required hospitalisation and one died due to salicylate toxicity. Two infants suffered convulsions and serious respiratory conditions, while three boys between four and 10 years of age developed gynecomastia (swelling of breast tissue) due to hormone-like effects of essential oils.
Compounds present in essential oils can alter the effects of prescription drugs and can also be toxic if ingested or applied to broken skin.
What does the evidence say?
Two theories exist to explain the effects of aromatherapy in the body. The first states that compounds found in essential oils have a direct effect on our health by affecting bodily functions, acting directly on the nervous system and the organs it controls. The olfactory system is connected to other functions of the central nervous system, including memory; however, research carried up to date has not conclusively shown that odours can influence organ function through their effect on the nervous system.
The second theory, known as the psychological theory, states that fragranced compounds have a psychological effect that promotes a sense of wellbeing, acting on several brain centres that affect perception, cognition and behaviour. Finding an odour pleasant or unpleasant can determine the mood response to it, as can belief and expectation of the properties of the odour: studies show that people respond to the suggestion that an ambient odour is relaxing independently of what the odour is. The psychological theory is considered as the best explanation for how aromatherapy can improve someone’s wellbeing.
The results obtained in aromatherapy studies vary considerably among different laboratories, suggesting that the different composition of the essential oils can influence their effects. The extraction techniques can vary among manufacturers as well, so that the exact components present in essential oils are not standardised. The total amount of active compound/s delivered to each person will also depend on the amount of essential oil used, as well as the temperature, size and air flow of the room it’s being administered in. For these reasons, it is difficult to standardise the therapy.
Another issue with aromatherapy trials is that the use of placebo is complicated, as the whole point of the therapy is to provide a characteristic fragrance.
A systematic review of seven studies including 428 dementia patients found no conclusive proof of a beneficial effect of aromatherapy on dementia. Participants were less agitated in the aromatherapy group compared to the placebo group in two studies, while three other studies found no difference in participants’ levels of agitation. The quality of the evidence was considered to be very low.
Another review assessed 16 studies (1,036 participants) evaluating the effects of aromatherapy on post-operative nausea and vomiting. Patients in the aromatherapy group had similar frequency and severity of nausea compared to those in the placebo control, although they were less likely to need antiemetic drugs. Again, the evidence was considered as low quality. A mathematical analysis of the data from the studies found that inhalation of isopropyl alcohol (rubbing alcohol) had a significant effect in reducing nausea severity compared to standard antiemetics.
The effect of aromatherapy massage in cancer patients was studied in a review of eight trials involving 678 patients. Six studies found increased relief from pain and anxiety in the aromatherapy massage group compared with no massage; it should be noted here that massage has been shown to be effective in reducing anxiety by itself. The remaining two trials found no further benefit in pain relief, anxiety, depression and quality of life by adding aromatherapy to massage.
Nine studies involving 644 patients analysed the effects of aromatherapy in postoperative pain management. Five trials found a beneficial effect of aromatherapy compared to placebo, while four found no significant differences between groups. A systematic review of studies in pain of different origins combined results from 12 studies and 1019 patients. The analysis suggested there was a beneficial effect of aromatherapy for pain relief, but the effect was very small and it was difficult to establish whether it was clinically relevant. Analysis of two trials including 535 patients found no difference between aromatherapy and placebo groups in pain intensity during labour, use of pharmacological pain relief, length of labour or caesarean section.
Conclusion
Aromatherapy can help improve mood and a general sense of wellbeing, which could be helpful in patients suffering from stress and anxiety. It also appears to be helpful in the prevention of nausea and vomiting. Aromatherapy is generally safe although serious adverse effects have been reported in children.
Alternative therapies
- What the evidence says
- Acupuncture
- Chiropractic
- Homeopathy
- Reiki
- Aromatherapy
- Why people use alternative therapies
