Eucalyptus is a tree. Its leaves and oil have been consumed, chewed, and applied to the skin for many conditions.

Eucalyptus contains many different chemicals. These chemicals might have various effects in the body. Also, some research suggests that eucalyptus may have activity against bacteria and fungi.

People use eucalyptus for many conditions including asthma, bronchitis, flu (influenza), and many others, but there is no good scientific evidence to support these uses.

There is interest in using eucalyptus for a number of purposes, but there isn’t enough reliable information to say whether it might be helpful.

When taken by mouth: People often consume eucalyptus as a flavoring in small amounts in foods. It’s possibly safe to take eucalyptol, a chemical that is found in eucalyptus oil, daily for up to 12 weeks.

But it is unsafe to take pure eucalyptus oil by mouth. Taking only 3.5 mL (less than one teaspoon) of the pure oil can be fatal. Eucalyptus oil can cause nausea, vomiting, and diarrhea. Eucalyptus poisoning can cause stomach pain, dizziness, muscle weakness, feelings of suffocation, drowsiness, seizures, and coma.

When applied to the skin: It’s possibly unsafe to use pure eucalyptus oil. It can cause serious problems with the nervous system. There isn’t enough reliable information to know if diluted eucalyptus oil is safe.

When inhaled: There isn’t enough reliable information to know if eucalyptus oil is safe when inhaled as aromatherapy.

Special precautions & warnings:

Pregnancy and breast-feeding: People often consume eucalyptus as a flavoring in small amounts in foods. But there isn’t enough reliable information to know if eucalyptus oil is safe to use when pregnant or breast-feeding.

Children: People often consume eucalyptus as a flavoring in small amounts in foods. But it is likely unsafe for children to take eucalyptus oil by mouth, apply it to the skin, or inhale it. There are reports of seizures and other nervous system side effects in infants and children who were exposed to eucalyptus oil.

Cross-allergenicity: Some people who are allergic to other essential oils might also be allergic to eucalyptus oil.

Surgery: Since eucalyptus might affect blood sugar levels, there is concern that it might make blood sugar control difficult during and after surgery. Stop using eucalyptus at least 2 weeks before a scheduled surgery.

Moderate

Be cautious with this combination.

Amphetamines

Inhaling eucalyptol, a chemical found in eucalyptus oil, might reduce the levels of amphetamines in the blood. In theory, the effectiveness of amphetamines may be reduced in people who inhale eucalyptol.

Medications changed by the liver (Cytochrome P450 1A2 (CYP1A2) substrates)

Some medications are changed and broken down by the liver. Eucalyptus might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2C19 (CYP2C19) substrates)

Some medications are changed and broken down by the liver. Eucalyptus might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)

Some medications are changed and broken down by the liver. Eucalyptus might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)

Some medications are changed and broken down by the liver. Eucalyptus might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications for diabetes (Antidiabetes drugs)

Eucalyptus might lower blood sugar levels. Taking eucalyptus along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.

Pentobarbital (Nembutal)

Inhaling eucalyptol, a chemical found in eucalyptus oil, might reduce the amount of pentobarbital that reaches the brain. In theory, the effectiveness of pentobarbital may be reduced in people who inhale eucalyptol.

Herbs and supplements that might lower blood sugar

Eucalyptus might lower blood sugar. Taking it with other supplements with similar effects might lower blood sugar too much. Examples of supplements with this effect include aloe, bitter melon, cassia cinnamon, chromium, and prickly pear cactus.

Herbs that contain hepatotoxic pyrrolizidine alkaloids (PAs)

Some supplements contains PAs, dangerous chemicals that can harm the liver. Taking eucalyptus along with supplements that contain PAs might increase the chance of developing serious side effects, including liver damage and cancer. Examples of supplements containing PAs include alkanna, butterbur, coltsfoot, comfrey, and groundsel.

There are no known interactions with foods.

There isn’t enough reliable information to know what an appropriate dose of eucalyptus might be. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult a healthcare professional before using.

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To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.

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