Using essential oils safely

Essential oils are concentrated. A single drop can represent a great deal of plant material, and that concentration is the whole of the safety question — everything below follows from it.

This is the part of the subject where accurate information does genuine good, because the harms are not hypothetical. They are burns, permanent allergies, asthma attacks, poisoned children, poisoned cats and house fires, and almost all of them come from advice that sounded gentle because the product was natural.

Never swallowed

Essential oils are not food, whatever a label says, and accidental ingestion of as little as a teaspoon has been fatal. As little as two millilitres of eucalyptus oil — well under half a teaspoon — can seriously poison an infant.

That makes storage the single most useful precaution in the house: high up, out of sight, in the original bottle, ideally with a child-resistant closure, and not on a bathroom shelf at toddler height. Essential oils smell pleasant and many come in small coloured bottles that look like something to drink.

If an essential oil has been swallowed:

• Rinse the mouth out.
• Do not try to make the person sick, and do not give them anything to drink until told to. Both raise the risk of oil entering the lungs, which is the serious injury.
• Ring 999 if the person is drowsy, having difficulty breathing, or has collapsed. Otherwise ring NHS 111 straight away, and have the bottle to hand.
• Symptoms can begin within half an hour and sometimes appear up to four hours later, so somebody seeming fine is not a reason to wait.

Dilution, and what the figures are

Essential oils are not applied neat to skin. "Neat" appears in a good deal of older writing and it causes chemical burns and sets up allergies.

Oils are diluted in a carrier — a plain vegetable or nut oil — and the concentrations used on skin are low single-figure percentages. In practice that means around one to two per cent for ordinary use, with something like five per cent treated as an upper limit rather than a target. One per cent is roughly one drop of essential oil in five millilitres of carrier. Less on the face, and considerably less for children and for older people with thinner skin.

A patch test is worth the trouble before using anything new over a larger area: a small amount at about twice the strength intended, on the inner forearm, left for a day or two.

If undiluted oil gets on skin, wash with soap and water rather than water alone — oils are not water-soluble and rinsing moves them around. In the eyes, rinse under gently running water for a full fifteen minutes, from the inner corner outwards, and get seen if there is any lasting pain or blurring.

Sensitisation, which is permanent

This is the risk people least expect. Repeated skin exposure can create an allergy that did not exist before, and once established it does not go away. It also tends to generalise: someone sensitised to one oil frequently reacts to others sharing the same constituents, and to perfumed products generally.

Oxidised oil is substantially more sensitising than fresh. Citrus and pine oils oxidise fastest once opened, which is the practical reason behind the storage advice under choosing and storing essential oils: an old bottle is not merely weaker, it is more likely to cause a reaction.

Sunlight, and the oils that react with it

Several expressed citrus oils — bergamot, lemon, lime, bitter orange and others, along with angelica — contain furocoumarins, which react with ultraviolet light on the skin and can produce a burn hours after application, sometimes a severe one with lasting pigmentation.

So skin treated with these should be kept out of sunlight and off sunbeds. It also means that advice to put oils on skin that has already had too much sun has the mechanism exactly backwards: St John's wort infused oil is itself photosensitising, and belongs nowhere near sunburn.

Inhaling these oils carries no such risk. It is only a skin-and-light problem.

Children

The margin for error is much narrower in children, and most of the harm in this field happens to them.

No essential oils on babies. Peppermint should not be used with children under about six. Eucalyptus and the other oils rich in strong-smelling volatile constituents can cause breathing difficulty in young children, including around the face and chest where they are most often applied. Oils are not a treatment for colic, teething or a cough, and advice recommending them for an "irritable child" or a "colicky infant" should be disregarded entirely.

Diffusers do not belong in a baby's or young child's bedroom, and bottles do not belong anywhere a child can reach.

Pregnancy, breathing and other circumstances

Pregnancy and breastfeeding. Constituents cross the placenta, the evidence is thin, and the sensible approach is to use little, dilute well, and ask a midwife — several NHS maternity services do use aromatherapy and will advise. Essential oils are not a remedy for morning sickness.

Asthma and airway conditions. Inhaled essential oils can trigger asthma and worsen other airway problems. This matters most with diffusers, because diffusing in a shared room makes the decision on someone else's behalf.

Epilepsy. A number of oils are traditionally avoided, and it is worth asking rather than assuming.

Medication. Anyone on prescribed treatment who intends to use oils on skin regularly is reasonable to mention it, particularly where skin conditions or anticoagulants are involved.

Animals, and cats especially

This is routinely left out of aromatherapy writing and it causes real veterinary emergencies. The RSPCA's position is that essential oils are hazardous to cats.

Cats metabolise these compounds poorly compared with people, so exposure accumulates. Tea tree oil is the most dangerous of the common ones. Signs of a problem include lethargy, loss of appetite, vomiting or diarrhoea, drooling, difficulty breathing, tremors, unsteadiness or weakness in the hind legs, and in serious cases seizures or collapse. Some signs appear late.

Dogs are also at risk, and birds are extremely sensitive to anything airborne. The common mistake is running a diffuser in a room an animal cannot leave. A cat that has been in a room with a diffuser and seems unwell, or that has had oil on its coat, should see a vet rather than be watched.

Steam and vapour for a blocked nose

One use of these oils has a long history and a reasonable safety record, and it is worth separating clearly from the claims made elsewhere about treating illness. Inhaling menthol, eucalyptus or pine vapour when the nose is blocked is a thoroughly ordinary thing to do, and it is not what the warnings above are aimed at.

What it does is also fairly well understood. Menthol and eucalyptol act on the cold receptors in the lining of the nose, which produces a strong sensation of clearer, cooler airflow. Measured nasal airflow changes rather little. The relief is in how breathing feels rather than in how open the airway actually is — which is genuine relief when a nose is blocked, and is not the same thing as shortening a cold, treating a chest infection or preventing the next one.

Licensed products exist for this and come with instructions worth reading: vapour rubs and inhalant capsules containing menthol, eucalyptus oil and camphor. The age limits on them are not decoration. Camphor-containing rubs are not for children under two, and camphor is properly toxic if swallowed.

The practical points, using oils directly:

• A few drops, not ten. More vapour is not better and strong concentrations irritate the airway.
• Warm water rather than boiling, or better still a tissue, a handkerchief or the corner of a pillowcase, which avoids the hot water entirely. Steam inhalation over a bowl is the commonest route to a serious scald, as below.
• Short sessions in a ventilated room, and not continuously through the night.
• Nothing left within reach of a child — neither the bowl nor the bottle.
• Not for anyone with asthma without checking first, for the reasons set out above, and not around a cat.

And the limit on all of it: breathlessness, a fever that will not settle, chest pain, coughing up blood, or a cough running on for weeks is not a job for a bowl of hot water. That needs seeing.

Diffusers

Short sessions in a ventilated room — something like fifteen minutes in an hour rather than all day. Never in a room that a child, an animal or a person with asthma cannot leave. Water-based ultrasonic diffusers need their water changed and the unit cleaned, or they grow their own problems.

Fire and scalds

Essential oils are flammable, and this gets forgotten because they are sold as a wellbeing product.

Oils are never added to a lit candle or to melted wax with the intention of relighting it; that is a flare-up waiting to happen. They do not go onto a light bulb or a hot lamp, near a hob, or onto cloth left near a heat source. A pan of water simmering with oils in it should not be left unattended.

Steam inhalation over a bowl of boiling water is a scald risk and has caused serious burns to children. It is not something to set up with a child in the room, and a few drops is the order of quantity involved rather than ten.

One thing that is simply never done

Essential oils, hydrosols and floral waters do not go inside the body. That includes douching, which some older aromatherapy writing recommends outright.

Douching is harmful in its own right, with or without added oils: it disturbs the normal bacterial balance of the vagina and is associated with infection rather than cleanliness. Every health body advises against it. Adding a concentrated plant extract to it compounds one bad idea with another, and tea tree oil in particular has no business there. The fuller picture is under vaginal thrush, which is the condition it is most often recommended for.

If something goes wrong

Poisoning or a serious reaction: 999 if someone is drowsy, struggling to breathe or collapsed, otherwise NHS 111. A reaction on the skin: stop using the product, wash it off, and see a pharmacist or GP if it is not settling — a persistent reaction is worth patch testing, since a sensitisation is permanent and worth knowing about. An affected animal: a vet, promptly.

A product making medical claims, or sold as safe to swallow, is a matter for Trading Standards.

See also aromatherapy for what the evidence does and does not support, and essential oils, absolutes and hydrosols.