Aromatherapy

Aromatherapy is the use of concentrated plant extracts — essential oils — for their smell and, in some practices, applied to the skin diluted in a carrier oil during massage. It is among the most popular complementary practices in Britain, and among the most oversold.

Two things can be said about it honestly, and this article is largely about keeping them apart. A pleasant smell and an hour of quiet genuinely make many people feel better, which is worth having. Aromatherapy does not treat illness, and the list of conditions it is claimed to treat is long, confident and unsupported.

What is actually happening

Smell reaches the brain by an unusually direct route. Odour molecules bind to receptors high in the nose, and the signal travels to the olfactory bulb and from there into structures involved in emotion and memory without first passing through the thalamus, as most sensory information does. That is a real anatomical feature and it is why a smell can produce a feeling or a memory before it has been identified.

It is also where most writing on aromatherapy stops thinking. That the pathway exists does not establish that any particular oil produces any particular effect, and it certainly does not establish an effect on blood pressure, immunity or infection. A smell that someone finds pleasant can change their mood; that is the mechanism, and it is a modest one.

Applied to the skin, some constituents of essential oils are absorbed in small quantities. This is sometimes offered as evidence of a systemic therapeutic effect. It is better understood as the reason the safety precautions in using essential oils safely exist.

What the evidence shows

Aromatherapy has been studied a great deal, which makes the answer unusually clear.

A 2024 evidence synthesis by Cochrane Australia, commissioned to inform government health policy, pooled the randomised trials across seven outcomes — pain, nausea and vomiting, sleep quality, fatigue, emotional and mental health, quality of life, and physical function — in populations including people with cancer, dementia and chronic musculoskeletal pain, and people undergoing surgery or in labour. Its conclusion was that it is not possible to draw conclusions about the effects of aromatherapy with confidence for any condition or outcome, with the certainty of evidence judged low or very low throughout, and with risk of bias, inconsistent results and probable selective reporting of favourable findings.

Within that, a few low-certainty signals pointed towards possible improvement in sleep quality, quality of life and physical function. Set against them, the same body of evidence suggested little or no effect on agitation in people with dementia, or on mental health in people with cancer — two of the uses most often claimed.

So the honest position is not that aromatherapy has been shown to do nothing. It is that after a great many trials, nothing has been shown with any confidence, and the pattern of the better-conducted studies is not encouraging. Where something that pleasant and that widely used has been tested this much and produced results this thin, the most likely explanation is that the effect is small, non-specific, and largely about feeling comfortable.

Which is a real thing. It is simply not a treatment.

The claims to disregard

These all circulate widely, and none of them is supported:

• That it lowers blood pressure, or improves the functioning of the immune system.
• That particular oils treat asthma or bronchitis. Inhaled essential oils can provoke asthma, which makes this the most backwards claim in the field.
• That any oil acts as an antidepressant, regulates menstrual cycles, or works as an aphrodisiac.
• That oils heal wounds, regenerate tissue or reverse ageing.
• That a bath or a massage is a reasonable substitute for seeing a doctor about a symptom.

There is also a regulatory point worth knowing. In the UK, a product sold with claims to treat, prevent or cure a disease is making a medicinal claim, and medicinal claims require a licence. A bottle of oil or a shop making such claims is not simply being enthusiastic; it is making a claim it is not entitled to make, and that is reportable to Trading Standards.

"Natural" does not mean gentle

The commonest argument in favour of essential oils is that they are natural, and therefore safer than synthetic fragrance. This is the reverse of the truth, and it is worth being specific about why.

Fragrance ingredients that must be declared on cosmetic labels because they commonly cause allergic reactions are, for the most part, constituents of essential oils: linalool and linalyl acetate from lavender, limonene from citrus, geraniol and citronellol from rose and geranium, citral from lemon and lemongrass, eugenol from clove, pinenes and terpinene from pine, eucalyptus and tea tree. The EU is expanding that list from twenty-six substances to around eighty for products placed on the market from mid-2026.

Essential oils are among the more frequent causes of allergic contact dermatitis from cosmetics. They are not inert because a plant made them — digitalis and nicotine are also natural — and a concentrated extract is further from a plant than it sounds.

Where it legitimately sits

Some NHS services, particularly in palliative care, hospices and maternity, offer complementary therapies including aromatherapy massage. That is not a contradiction of anything above. It is offered for comfort, as part of looking after someone, and it is not presented as treating the underlying illness.

That is the right frame for aromatherapy generally. Something pleasant, worth doing for its own sake, with a plausible and small effect on how a person feels. It stops being harmless at the point where it is used instead of something that works, or applied in ways that cause injury.

The rest of this subject is in three parts: essential oils, absolutes and hydrosols, which explains what the various products actually are; using essential oils safely, which is the one with real practical value; and choosing and storing essential oils.

See also alternative therapies.