From the BBC website...

What is it?

Aromatherapy is the therapeutic use of essential oils, from flowers, trees and shrubs and their fruits, blooms, leaves, stems and roots.

The oils are obtained by steam distillation, expression (squeezing the oil from peel), maceration (immersing the plant in hot oil to release the essence) or enfleurage (pressing flowers between oiled glass plates).

What does it involve?

Essential oils are usually either massaged into the body, to be absorbed through the skin, or inhaled by means of vaporisers. They may also be added to steam inhalations or baths, added to compresses or spread throughout a room with diffusers.

Who practises it?

Nurses, doctors, massage therapists, osteopaths and trained aromatherapists are some of the people who practise aromatherapy.

What's it used for?

It's often used to relieve stress, headaches, insomnia, tension and pain, and to aid relaxation and general wellbeing. It's increasingly being used in cancer care and in sports therapy.

What's the evidence?

Research on different oils has identified their individual constituents and different effects from stimulant to sedative.

Clinical trials have confirmed that aromatherapy can aid relaxation and help relieve anxiety.

A randomised, controlled trial of 288 cancer patients, in four UK cancer centres and a hospice, showed that aromatherapy helped to provide short-term relief of anxiety and depression in those patients undergoing chaemotherapy.

However, in the long-term, only a decrease in self-reported anxiety was evident and the study did not distinguish between the effects of different oils, the massage and interaction with a sympathetic therapist.

Other studies have suggested that aromatherapy may be helpful for conditions such as bronchitis, alopecia and agitation associated with dementia. But some of the studies have flaws or have not had their results repeated, so more research is needed to establish the effectiveness of different oils.

The NHS Complementary and Alternative Medicine Specialist Library lists some research on aromatherapy. It's aimed at health professionals, but much of it is accessible in plain language summaries.

There is one review study on aromatherapy and cancer care in the Cochrane Reviews, which provide independent evidence on specific healthcare topics. Use the search box to search for aromatherapy.

Scientific research concerning the biological activity of essential oils and their components is available at the Essential Oil Resource.

How popular is it?

Aromatherapy is one of the most popular forms of complementary therapy and is widely used by people buying over-the-counter oils, and by health professionals in a range of settings.

How does it work?

Scents from essential oils can stimulate olfactory (smell) receptors in the nose, and brain scans have shown that this can then trigger activity in certain areas of the brain linked to mood and memory.

Components of essential oils may also be absorbed via the skin into the bloodstream and are then thought to influence the nervous system, mental state and emotions, and possibly even organ function, although the exact mechanism for this is still unclear.

What happens?

Diagnosis: Aromatherapists do not make medical diagnoses unless they're medically qualified, so if you're in any doubt about your condition you should consult your doctor.

Treatment: The aromatherapist will take a medical history and then determine which oil, or combination of oils, will be the most beneficial for you. You'll normally be asked to undress to your underwear and then be covered with towels in a warm room.

The oils will be diluted in a carrier oil, such as almond or grape seed, and then massaged into your neck, shoulders and upper back, or given as a full body massage, or a facial.

Various massage techniques may be used although Swedish massage is the most common.

Time taken: An aromatherapy massage can last from 20 to 90 minutes depending on whether its a partial or full body massage.

Techniques: Some aromatherapists also use manual lymphatic drainage and/or acupressure techniques as part of their treatment.

Is it safe and are there any side-effects?

Common, mild side-effect - slight drowsiness. You should not drive or operate heavy machinery immediately after treatment.

Occasional side-effects - essential oils are very concentrated and some cause irritation if applied directly to the skin. They should always be diluted in a vegetable carrier oil before being applied to the skin. Contact with the eyes should also be avoided to prevent irritation. Some citrus oils can increase the skin's sensitivity to light, making it more prone to pigmentation.

Severe side-effects – the oils should not be swallowed or otherwise taken internally, unless under expert medical supervision, as they may be toxic. Allergic reactions are also possible. It's best to test for this by applying a small amount of diluted oil on the back of the wrist or ear lobe as test before using it fully.

Certain oils may also interact with prescribed medicines. Get advice from your doctor or aromatherapist if taking medication.

How many treatments will I need?

People who have aromatherapy for relaxation and pleasure may have a treatment every week.

Treatments for ailments, such as respiratory problems, are usually weekly over several sessions and then gradually spread over increasing intervals to fortnightly or monthly follow-ups.

When should I not have aromatherapy?

Certain essential oils may not be used if you are pregnant, breastfeeding, have asthma or high blood pressure. In such cases, always get advice on appropriate oils and massage techniques from a trained aromatherapist.

Aromatherapy should not be used with infants and very young children, or immediately after surgery. It is also not advised if you have epilepsy, varicose veins, deep vein thrombosis or contagious skin conditions. Areas of broken skin should also be avoided.

How much will it cost?

Aromatherapy sessions usually cost from £25 to £90 depending on whether you have a full body or partial massage. Aromatherapy treatments on the NHS are usually free or subsidised. Private health insurance does not usually cover aromatherapy

How can I find a qualified practitioner?

The new voluntary, self-regulatory body for aromatherapists in the UK is the Aromatherapy Council. It's in the process of establishing a directory of members who are properly qualified and who follow its code of professional practice.

Its site has links to the various individual aromatherapy associations active in the UK, which currently all operate their own directories of qualified practitioners.

Trained aromatherapists can also be found via the Aromatherapy and Allied Practitioners' Association.

What if I have a problem?

Talk over any concerns with your practitioner, but if you have a more serious complaint use the formal complaints procedure of your practitioner's professional body.

A medical opinion

Dr David Peters, professor of integrated healthcare at Westminster University, London, says: "Doctors understand the benefits of relaxation and believe that aromatherapy may help with this. However, responses to different oils and their scents are very personal and not all aromatherapists agree on the properties of various oils. More research is needed on the specific therapeutic effects of different oils."

This article was written by Jacqueline Young, medically reviewed by Dr Rob Hicks and first published in February 2007.