Eucalyptus: Everything You Need to Know

Medically reviewed by Allison Herries, RDN

Eucalyptus is a large genus with more than 660 different types of plant species belonging to the Myrtle family (Myrtaceae).

While Eucalyptus is native to Australia, Tasmania, and surrounding islands, this group of plants also grows in other parts of the world.

Eucalyptus globulus (E. globulus), also known as southern blue gum, is a common eucalyptus tree.

E. globulus has several plant chemicals; its leaves make eucalyptus oil. Eucalyptus oil also has many substances—but mostly eucalyptol. These plant chemicals make E. globulus effective.

This article will highlight E. globulus, including its health claims, side effects, dosing requirements, and more.

Dietary supplements are not regulated the way drugs are in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement tested by a trusted third party, such as U.S. Pharmacopeia ( USP), ConsumerLab.com, or NSF International.

However, even if supplements are third-party tested, they are not necessarily safe for all or effective in general. Therefore, talking to your healthcare provider about any supplements you plan to take and asking about potential interactions with other supplements or medications is important.

• Active ingredient(s): Flavonoids, alkaloids, tannins, phenylpropanoids, eucalyptus oil

• Alternate names(s): Eucalyptus, Eucalyptus globulus, E. globulus, Tasmanian blue gum, eucalyptus oil, eucalyptol, 1,8-cineole, essential oils

• Legal status: Legal as an essential oil, supplement ingredient, and substances added to food as a flavoring agent

• Suggested dose: May vary based on the dosage form and medical condition

• Safety considerations: Possible side effects, interactions, and special considerations for children, pregnancy, and breastfeeding

Uses of of Eucalyptus

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.

While more, extensive research is necessary regarding efficacy (its ability to produce a desired effect), people use E. globulus or eucalyptus oil to treat various health conditions.

Research is most robust for E. globulus's effects concerning the following:

• Antioxidant effects

• Cold symptoms

• Pain

• Relaxing effects

Antioxidant Effects

In one in vitro lab study (tests performed outside a living organism, in a lab setting, such as in a test tube), extracts from E. globulus leaves reduced oxidative stress in SH-SY5Y cells (cells that serve as a model to study neurodegenerative disorders).

In general, oxidative stress is when there aren't enough naturally occurring antioxidants in your body to attack unstable atoms known as free radicals. Free radicals can damage components and systems within the body, including DNA.

Study results suggest the positive antioxidant effects of E. globulus leaf extracts.

However, as this study was on a cell line, future high-quality clinical trials are needed to determine if these antioxidant effects apply to humans.

Cold Symptoms

In a review article, data from several studies supported inhaling (breathing in) eucalyptus oil in children or adults to relieve cold symptoms, such as nasal congestion, nighttime coughing, and sleep problems.

While these results were positive, many clinical trials studied the effects of aromatic ointments containing eucalyptus oil mixed with other essential oils.

For this reason, it's difficult to know the effects of just eucalyptus oil. Also, some clinical trials only had a small number of participants, meaning the samples were too small for the results to be conclusive.

In general, further research with high-quality, larger studies is still necessary to better evaluate the effects of eucalyptus oil.

Pain

A 2021 systematic review (a methodical review of a collection of studies) included a small clinical trial on the effects of an ointment containing eucalyptus oil.

When applied to the study participants' forearms, the eucalyptus oil–based ointment increased blood flow to the application sites.

This suggested that the ointment may temporarily relieve minor muscle aches. Although the results were positive, the ointment contained ingredients and eucalyptus oil.

Therefore, it's difficult to determine if the benefits came from the eucalyptus oil or the other ingredients in the ointment.

In another small clinical trial, participants inhaled eucalyptus oil for 30 minutes three days after total knee replacement surgery. By the end of the study, participants reported less pain and had decreased hypertension (high blood pressure).

In another small study, a group of participants with rheumatoid arthritis (RA) inhaled eucalyptus oil for five minutes three times daily for one month. In the third and fourth weeks of using eucalyptus oil, this group reported less pain and improved quality of life.

Further research with a larger group of participants is needed to determine eucalyptus oil's effects fully.

Relaxing Effects

In a small study conducted on 62 preoperative individuals, eucalyptol and eucalyptus oil group participants reported less anxiety before their procedure than participants not using the oils—with eucalyptol showing a greater effect than eucalyptus oil.

Regarding this study, it should be noted that the participants inhaled eucalyptus oil (vs. taking it by mouth) before a medical procedure that also used local anesthesia.

Eucalyptol is a substance in eucalyptus oil. While eucalyptus oil contains numerous substances, eucalyptol makes up a big percentage of the components in eucalyptus oil.

These results are promising, but additional research with higher quality and larger studies is still necessary.

What Are the Side Effects of Eucalyptus?

As with many medications and natural products, E. globulus and eucalyptus oil can have side effects.

Common Side Effects

Eucalyptus oil is on the FDA's list of approved substances added to food, but it is often used in small amounts.

More research on E. globulus and eucalyptus oil safety is necessary, but common side effects include stomach upset and nausea.

Severe Side Effects

Possible serious side effects may include:

• Severe allergic reaction: A severe allergic reaction is a serious side effect possible with any medication or natural product. If you're having a severe allergic reaction, symptoms may include breathing difficulties, itchiness, and rash.

• Seizures: Large amounts of eucalyptus oil taken by mouth may increase your risk of seizures.

• Slow breathing rate: Too much eucalyptus oil by mouth may dangerously slow your breathing rate, increasing the risk of death.

• Slowing effects on the central nervous system (CNS): The CNS includes your brain and spinal cord. Taking excessive eucalyptus oil by mouth may slow down the activity of your CNS, and this will likely worsen eucalyptus oil's other side effects, such as a slow breathing rate.

If you're having a severe allergic reaction or if any of your symptoms feel life-threatening, call 911 and get medical help right away.

Precautions

A healthcare provider may advise against E. globulus use if any of the following applies to you:

Severe allergic reaction: Avoid E. globulus if you have a known allergy to it or its ingredients or parts, such as eucalyptus oil. If you're unsure if it's safe for you, ask a pharmacist or healthcare provider for a complete list of the ingredients.

Pregnancy and breastfeeding: E. globulus product labels are unlikely to target pregnant or breastfeeding people.

Moreover, more research on E. globulus and eucalyptus oil safety is necessary for these groups. Before using E. globulus or eucalyptus oil, contact a healthcare provider to discuss the benefits and risks.

Adults over age 65: While older adults have participated in a eucalyptus oil–based study, more extensive research with more older individuals is still necessary to assess the safety of E. globulus and eucalyptus oil in this age group.

Moreover, some older adults may have a higher likelihood of medication side effects. For this reason, use caution with E. globulus and eucalyptus oil.

Children: Very few E. globulus product labels directly target infants and children.

While children have participated in eucalyptus oil–based studies, sample sizes were small. Therefore, higher-quality, larger studies are necessarily better for evaluating the safety of E. globulus and eucalyptus oil.

Talk with a healthcare provider if you're considering E. globulus or eucalyptus oil for your child.

Blood pressure: E. globulus and eucalyptus oil may affect your blood pressure.

For this reason, a healthcare provider may want to closely monitor you and make the necessary adjustments to your blood pressure medications if you use eucalyptus.

Lung conditions: E. globulus and eucalyptus oil may affect your breathing.

A healthcare provider may want to closely monitor you and adjust your medications accordingly if you have a lung condition, such as asthma or chronic obstructive pulmonary disease (COPD).

Seizures: E. globulus and eucalyptus oil may raise your risk of seizures. If you have a history of seizures, a healthcare provider may advise against eucalyptus use or want to monitor you closely before adjusting your medications.

Animals: Toxicity from essential oils—like eucalyptus oil—is possible in animals. In animal studies, rats and mice experienced liver, kidney, and fertility problems.

In dogs and cats, there were reports of depression and muscle movement problems in one study. As a result, before using essential oils on or around animals, contact your veterinarian to discuss the benefits and risks.

Surgery: Because eucalyptus may affect blood sugar levels, there is a concern that it might make blood sugar control difficult during and after surgery.

Individuals should talk with their healthcare provider if they consider using eucalyptus oil before a medical procedure.

Dosage: How Much Eucalyptus Should I Use?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

While there are some studies on E. globulus or eucalyptus oil in humans, more research with high-quality clinical trials is still necessary.

For this reason, there are no guidelines on the appropriate dosage to use of E. globulus or eucalyptus oil for any condition.

The specific dose may vary based on the dosage form and medical condition. If you use E. globulus or eucalyptus oil, follow a healthcare provider's recommendations or product label instructions.

What Happens If I Use Too Much Eucalyptus?

More information about the safety, toxicity, and overdose of E. globulus and eucalyptus oil in humans is needed.

However, overdose symptoms with E. globulus and eucalyptus oil are likely similar to symptoms of its common and serious side effects—but are excessive and more severe.

For example, large amounts of E. globulus or eucalyptus oil by mouth will likely result in the following symptoms:

• Dangerously slow breathing rate

• Seizures

• Slow brain activity

• Death

Taking only 3.5 milliliters (less than 1 teaspoon) of pure eucalyptus oil can be fatal.

If you suspect you're experiencing life-threatening side effects, seek immediate medical attention.

Interactions

There is limited information about possible medication interactions with E. globulus or eucalyptus oil.

Possible interactions are based on the health claims or potential side effects of E. globulus and eucalyptus oil.

• Blood pressure medications: Breathing in eucalyptus oil may lower your blood pressure. This means E. globulus or eucalyptus oil might have additive effects with your blood pressure medications, such as Zestril (lisinopril), making their effects greater. Symptoms of low blood pressure include dizziness and fainting spells.

• Breathing medications: Taking eucalyptus oil by mouth may impact your breathing rate. E. globulus or eucalyptus oil may also interact with medications—like albuterol—for your lung condition.

• CNS depressants: Eucalyptus oil by mouth may slow down the central nervous system. For this reason, it may have additive effects with other CNS depressants, such as alcohol, Ativan (lorazepam), and opioid pain medications.

• Seizure medications: Eucalyptus oil by mouth may increase your risk of seizures. Therefore, E. globulus or eucalyptus oil might work against your seizure medications.
  

It is essential to carefully read a supplement's list of ingredients and nutrition facts panel to know which and how much of each ingredient is included.

Review this supplement label with your healthcare provider and discuss potential interactions with foods, other supplements, and medications.

How to Store Eucalyptus

Storage instructions may vary by product. Carefully read the directions and packaging label on the container.

Generally, medicines and supplements should be stored in a cool, dry place unless otherwise instructed. Keep your medications tightly closed and out of the sight and reach of children and pets, ideally locked in a cabinet or closet.

Discard after one year or as indicated on the packaging. Avoid putting unused and expired products down the drain or in the toilet. Visit the FDA website to learn where and how to discard all unused and expired medications.

You can also find disposal boxes in your area.

Ask a pharmacist or healthcare provider any questions about how to dispose of your medications or natural products.

If you plan to travel with E. globulus or eucalyptus oil, get familiar with your final destination's regulations. The United States Embassy and Consulate office might be a helpful resource.

Ask a healthcare provider how to travel with your medications or natural products if necessary.

Similar Supplements

E. globulus and eucalyptus oil have health claims of potentially relieving cold symptoms, decreasing pain, and lessening anxiety before a procedure.

Other similar supplements include:

• Melatonin: Melatonin may help relieve some anxiety before a procedure.

• Menthol: Menthol is a main component (ingredient or part) in peppermint oil, an essential oil. Menthol might also be commonly combined with eucalyptus oil to relieve cold symptoms, such as coughing.

• Omega-3 fatty acids: Omega-3 fatty acids from fish oil and foods like salmon and tuna may help people with RA pain.

• Vitamin C: Routinely taking vitamin C may help relieve your cold symptoms.
  

Don't combine multiple natural products until you first talk with a healthcare provider or pharmacist. Inquiring about possible interactions and side effects can ensure you give these supplements a fair trial at appropriate doses.

Frequently Asked Questions

What is the most common dosage form of E. globulus?

E. globulus is available in a few different dosage forms—with liquid being the most common.

Are any E. globulus products manufactured in the United States?

Yes. Manufacturers in the United States make E. globulus products.

Is E. globulus used as an insect repellent?

No. Some insect repellent products contain the oil of lemon eucalyptus from the Corymbia citriodora (C. citriodora) plant—not the E. globulus plant.

How do I use Eucalyptus globulus safely?

To safely use natural products—like E. globulus or eucalyptus oil—inform healthcare providers and pharmacists about other medications you're taking, including over-the-counter (OTC), herbal, natural medicines, and supplements.

Your healthcare provider can help you prevent possible medication interactions and side effects.

They can also ensure that you’re giving E. globulus or eucalyptus oil a fair trial at appropriate doses.

Sources of Eucalyptus & What to Look For

There are a few different sources of E. globulus or eucalyptus oil.

Food Sources of Eucalyptus

Eucalyptus oil is a substance from the leaves of E. globulus, which is naturally available as a plant.

The U.S. Department of Agriculture (USDA) generally categorizes Eucalyptus globulus as food.

Eucalyptus oil is also on the FDA's list of substances added to food.

It's added to food as a flavoring agent—but likely in small amounts.

Eucalyptus Supplements

E. globulus is likely commonly available in a liquid form as eucalyptus oil. Other dosage forms of E. globulus may also include:

• Capsules

• Tablets

• Tea bags

Some of these other forms come with additional ingredients. Vegetarian options should be available.

What will work for you will depend on your preferences and what you hope to get from the product regarding effects. Each product may work a bit differently, depending on the form.

Following a healthcare provider's recommendations or label directions is essential.

Summary

Eucalyptus is a large group of plants, including E. globulus. The eucalyptus oil from E. globulus has several health claims, which may include relieving cold symptoms, reducing pain, and lessening anxiety before a procedure.

Since further extensive research is necessary, it's important not to delay the diagnosis and treatment of your medical conditions.

Before using E. globulus or eucalyptus oil, involve a pharmacist or healthcare provider to help you safely achieve your health goals.