Herb & supplement monograph

Eucalyptus Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Eucalyptus interacts with medications. The heart of this page is the interaction list — every drug Eucalyptus is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Eucalyptus is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Eucalyptus Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Eucalyptus drug interaction appears low for most people, since none of its interactions have been confirmed in human studies. All listed interactions are rated moderate rather than major, and every one rests on animal or lab research only.

Interactions deserving the most attention

The combination most worth watching is eucalyptus leaf with diabetes medications, because animal research suggests eucalyptus may lower blood sugar and could add to the effect of these drugs. Animal studies also suggest that inhaling eucalyptol might reduce the effectiveness of amphetamines and pentobarbital by lowering the amount of drug reaching the blood or brain. None of these effects have been shown in people, but blood sugar control and sedative response are worth paying attention to if you use eucalyptus regularly.

What the rest of the list means

The long list of interacting medications looks alarming, but most of it comes from lab findings that eucalyptus oil might slow enzymes the body uses to clear many common drugs. That effect has not been reported in humans, so a listed interaction does not mean the combination is known to be harmful.

Check your medications against Eucalyptus

Based on HelloPharmacist’s Eucalyptus interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Eucalyptus

880 medications have a known interaction with Eucalyptus, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Eucalyptus using our pharmacist-reviewed interaction data.

AI summaries are generated from our Eucalyptus interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Eucalyptus combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Eucalyptus affects

Every type of medication (drug category) Eucalyptus is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 7 drug categories Eucalyptus interacts with

AmphetaminesAntidiabetes DrugsCytochrome P450 1a2 (cyp1a2) SubstratesCytochrome P450 2c19 (cyp2c19) SubstratesCytochrome P450 2c9 (cyp2c9) SubstratesCytochrome P450 3a4 (cyp3a4) SubstratesPentobarbital (nembutal)

Amphetamines

Theoretically, inhaling eucalyptol may reduce the effectiveness of amphetamines.
Animal research suggests that inhaling eucalyptol may reduce the levels of amphetamines in the blood.

Likelihood Possible Evidence D

Antidiabetes Drugs

Theoretically, eucalyptus leaf might increase the risk of hypoglycemia.
Animal research suggests that eucalyptus leaf might have hypoglycemic activity, and might have additive effects when used with antidiabetes drugs.

Likelihood Possible Evidence D

Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, eucalyptus might increase the levels of CYP1A2 substrates.
In vitro research suggests that eucalyptus oil might inhibit CYP1A2, although this has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2C19 (Cyp2C19) Substrates

Theoretically, eucalyptus might increase the levels of CYP2C19 substrates.
In vitro research suggests that eucalyptus oil might inhibit CYP2C19, although this has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, eucalyptus might increase the levels of CYP2C9 substrates.
In vitro research suggests that eucalyptus oil might inhibit CYP2C9, although this has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, eucalyptus might increase the levels of CYP3A4 substrates.
In vitro research suggests that eucalyptus oil might inhibit CYP3A4, although this has not been reported in humans.

Likelihood Possible Evidence D

Pentobarbital (Nembutal)

Theoretically, inhaling eucalyptol might reduce the effectiveness of pentobarbital.
Animal research suggests that inhaling eucalyptol reduces the level of pentobarbital that reaches the brain.

Likelihood Possible Evidence D

Monograph

Eucalyptus: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Eucalyptus is best known for its strong-smelling oil used in vapor rubs, inhalants, and lozenges to ease coughs and congestion. It may provide mild, short-term relief of cold symptoms, but the oil is toxic if swallowed and must never be taken by mouth undiluted. Talk to a pharmacist or doctor before using it, especially in children, during pregnancy, or while breastfeeding.

Scientific name: Eucalyptus globulus
Family: Myrtaceae
Part used: Leaves and essential oil
Common forms: Essential oil, inhalants/vapor rubs, lozenges, tea, capsules, topical creams

People commonly use it for

Cough and chest congestion
Colds and flu symptoms
Stuffy nose
Sore throat
Minor muscle and joint aches
Aromatherapy

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally safe in small amounts for inhalation or diluted topical use, but the undiluted oil can be poisonous if swallowed.

PregnancyLikely Safe

When used orally in amounts commonly found in foods. There is insufficient reliable information available about the safety of medicinal amounts of euc...

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally in amounts commonly found in foods. There is insufficient reliable information available about the safety of medicinal amounts of euc...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Eucalyptus is an evergreen tree native to Australia and a member of the myrtle (Myrtaceae) family. Its leaves have a strong, fresh, menthol-like smell and are the main food of koalas. Today eucalyptus is grown in many warm parts of the world.

The leaves and the oil pressed from them have a long history in traditional and folk medicine. People most often use eucalyptus to help with breathing problems like coughs, colds, and stuffy noses. You will find it in many over-the-counter products, including vapor chest rubs, inhalers, lozenges, mouthwashes, and aromatherapy oils.

The main active ingredient in the oil is a compound called eucalyptol (also called 1,8-cineole), which gives eucalyptus its sharp scent.

How it works

Eucalyptus oil is rich in eucalyptol (1,8-cineole). Laboratory and animal studies suggest this compound may have anti-inflammatory effects, may help thin and loosen mucus, and may have mild antimicrobial activity against some bacteria and fungi.

When inhaled, the strong aroma creates a cooling sensation in the nose and airways that can make breathing feel easier. When applied to the skin, it may produce a warming or tingling feeling that distracts from aches.

Keep in mind that many of these effects come from lab or animal research, so they do not always translate into clear benefits in people.

Effectiveness

Does Eucalyptus work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 28 uses evaluated

28 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Eucalyptus, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 28 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Acne