eucalyptus

What is eucalyptus?

Eucalyptus is the leaf and leaf oil of a tall evergreen tree. People use it for chest colds, a blocked nose, coughs and sore muscles. Most home use is a steam, a chest rub, or a weak leaf tea.

The honest verdict: the evidence is thin but not empty. Small trials of its main compound, cineole, point to mild help with coughs and stuffy sinuses. The essential oil is also a real poison if swallowed, and a few millilitres have harmed adults.

In the Caribbean it is called eucalipto in Cuba and the Dominican Republic, and ekaliptis in Haiti. The tree came from Australia and was planted widely. Long use in a tradition is not proof that a plant works, and it is not proof that it is safe.

How does eucalyptus work?

Most of the proposed action is credited to one compound, 1,8-cineole, also called eucalyptol.

In test tubes, cineole slows some bacteria and fungi. In animal and cell work it appears to calm inflammation (swelling) and thin mucus. Whether either of these happens in your airway is not settled.

In small human trials, cineole capsules eased cough and sinus symptoms a little. That is the strongest link we have. It does not tell us that steam from a bowl does the same thing.

The cool feeling in your nose is largely a nerve effect. Cineole triggers cold-sensing nerves, so air feels easier to draw in. In studies, measured airflow often changes very little.

On skin, eucalyptus rubs create warmth and a strong smell. That may distract from aching muscles. Deep effects on joints or muscle tissue have not been shown in people.

What forms does eucalyptus come in?

Eucalyptus is sold in forms that differ hugely in strength. The bottled oil is the strongest by a wide margin.

Dried leaf, brewed as a tea.

Fresh or dried leaf dropped into hot water for steam.

Essential oil, for a diffuser or vaporiser.

Chest rubs, balms and ointments holding eucalyptus oil.

Lozenges, cough syrups and mouthwashes with small flavouring amounts.

Capsules of purified 1,8-cineole, licensed as medicines in parts of Europe.

Bath products, soaps and pillow sprays.

The essential oil is meant for diluted use on skin or in air. It is not a drink. Lemon eucalyptus oil, used in insect repellents, comes from a different tree and is not the same product.

Where it comes from:

Eucalyptus was planted across the Caribbean after the tree was carried from Australia in the 1800s. Homes in Cuba, the Dominican Republic and Haiti took it up fast.

Healers boiled the leaves and had people lean over the steam under a cloth. This was used for colds, flu, blocked noses and fever.

Leaf baths were used for chills and body aches. Leaves were also hung in a room, or burned, where someone lay sick.

Similar customs appear in Puerto Rican and Jamaican home care. The leaves were often blended with ginger, lime or honey.

These records tell us what families valued and passed on. Records of tested results are far thinner.

What does eucalyptus help with?

• Blocked nose and chest congestion with a cold: This is the main Caribbean use, taken as steam over a pot of boiled leaves. Many people report that breathing feels easier within minutes. Studies suggest the feeling comes from cold-sensing nerves in the nose. Measured airflow often changes little. So it may make you more comfortable without clearing much mucus. It does not shorten a cold.
• Cough: Cineole is a common ingredient in cough syrups and lozenges in many countries. Small trials of cineole capsules in bronchitis reported fewer coughing fits than placebo. The trials were short, small, and several had industry funding. For leaf tea, there is no good human evidence either way.
• Sinus pressure and sinusitis: Cineole capsules have been tested in people with sudden sinus inflammation. Some trials reported milder headache, pressure and blocked nose after a few days. The effect size was modest and the studies were small. Larger, independent trials are missing. Steam alone has not been shown to clear a sinus infection.
• Sore throat: Eucalyptus flavours many throat lozenges and gargles. The cooling feeling can dull soreness for a short time. There is little human testing of eucalyptus by itself for throat pain. Most relief probably comes from sucking and from saliva. If a sore throat comes with high fever or trouble swallowing, it needs a doctor, not a lozenge.
• Muscle and joint aches, rubbed on skin: Caribbean leaf baths and modern chest rubs share this use. The oil makes skin feel warm and tingly. That counter-feeling can mask aching for a while. Human trials of eucalyptus alone for muscle or joint pain are few and weak. It does not treat the cause of arthritis or an injury.
• Asthma symptoms, as an add-on only: One small double-blind trial found cineole capsules let some people with asthma cut their steroid tablet dose a little. That result has not been repeated in large trials. It is not a reason to lower any asthma medicine on your own. Strong eucalyptus vapour can also trigger wheezing in some people. Talk to the doctor who manages your asthma first.

What are the side effects of eucalyptus?

• Skin redness, stinging or rash from the oil
• Burning eyes from vapour or splashes
• Headache
• Coughing or wheezing from strong vapour
• Nausea, vomiting and diarrhoea after swallowing
• Drowsiness and slurred speech after swallowing oil
• Seizures (fits) and coma after swallowing oil
• Slowed or stopped breathing in babies and toddlers
• Allergic rash in people sensitive to the oil

Good to know:

Most harm comes from swallowing the oil or putting too much on skin.

With steam and rubs, side effects are usually mild. Rash, stinging eyes, headache and coughing are the common ones. Stop if your skin reddens or burns.

Swallowing the essential oil is the dangerous route. Signs can start within 30 minutes. Vomiting, drowsiness, slurred speech and seizures have all been reported.

Children are harmed by far smaller amounts than adults. Oil placed under a small child's nose has caused breathing to stop.

How much eucalyptus should you take?

• Recommended daily: This page gives no personal dose. What follows is the kind of amount product labels carry. Leaf tea labels often list about 2 grams of dried leaf per cup. Two or three cups a day is a common label figure. Steam products often suggest a few drops of oil in a bowl of hot water. Chest rubs usually hold around 1 to 3 percent eucalyptus oil. Cineole capsules sold as pharmacy medicines in Europe are often 100 to 200 mg, up to three times a day. These are regulated drugs. Follow that label and your pharmacist. Never swallow neat essential oil. Around 3.5 mL has caused serious poisoning in adults. Much smaller amounts have harmed children.
• Best time of day: Timing does not matter much for how well it works. Many people use steam or a chest rub at night, because a blocked nose is worse lying down. The cooling feeling may help you settle. Avoid strong vapour right before exercise if you have asthma.
• With or without food: Tea and steam do not depend on meals. Cineole capsule labels often say to swallow them whole with a cold drink before food. Do not chew them, as the oil can burn the mouth. Oily capsules on an empty stomach cause burping and heartburn in some people.
• Time to effect: The cooling, open feeling in the nose starts within minutes of a steam or rub. In the cineole capsule trials, symptom changes took about three to four days to show up. It may also do nothing for you. Some people get no relief at all, and some find the smell makes them cough.
• How long to take it: Eucalyptus is a short-term comfort measure, not a daily habit. Steam and rubs are usually used for a few days, while a cold runs its course. Cineole capsule labels in Europe often cap use at about two weeks. If symptoms last more than a week, or get worse, stop and get checked.