The eucalyptus tree was one of the most valued botanical resources for Indigenous Australians. Eucalyptus was used not only in food and medicine but also in the manufacture of utensils.

Eucalyptus oil is the main component of eucalyptus leaves, the part of the plant that has nutritional value and medicinal properties. Modern science has confirmed eucalyptol, the oil’s main chemical, is responsible for the soothing benefits of eucalyptus. Numerous modern applications exist for eucalyptus oil in medicine, cosmetics, and aromatherapy.

The Botany of Eucalyptus

Eucalyptus is one of the tallest trees on earth, with an average height of 98 to180 feet. This fast-growing evergreen is native to Australia and Tasmania and belongs to the myrtle family (Myrtaceae) (1). There are more than 700 species of eucalyptus tree, but the most appreciated and thoroughly studied is Eucalyptus globulus, commonly called the Tasmanian blue gum (1, 2).

Eucalyptus leaves have different shapes and texture depending on their age (1, 2). Young leaves are round, blue-green-gray, and leathery, while older leaves turn long and sickle-shaped with a distinctive central vein (2). The leaves contain many oil glands, which release their oil when crushed and soaked in water. This oil can be used in aromatherapy to support the immune system, revitalize the body, and stimulate the senses (1, 2, 6).

Early Uses for Eucalyptus

Early Indigenous Australians possibly discovered eucalyptus’s beneficial properties during their period of hunter-gatherer intensification between 3000 and 1000 B.C. These people ate manna, a deliciously sweet sap exuding from holes in the eucalyptus tree trunk that dries into sugary, white drops and falls to the ground. People who lived along rivers and streams during this time made canoes from the bark of eucalyptus as well as spears, bowls, and utensils for eating (1).

After the British colonization of Australia in 1788, eucalyptus leaf spread throughout Europe. The first reports of eucalyptus oil being used as a topical chest rub or inhaled vapor can be traced back to the 18th century (3-6).

Health Benefits of Eucalyptus Essential Oil

Eucalyptus oil, obtained by steam distillation from fresh leaves, retains most of the health benefits of eucalyptus leaf (3-6). The oil is carefully processed (rectified) to remove chemicals that may irritate the respiratory tract.

The benefits of eucalyptus oil relating to respiratory health are well known. The ingredient has been widely used in many proprietary (patented) products, syrups, lozenges, nasal drops, and preparations for inhalation (4-12).

When diluted with almond oil, eucalyptus oil can be applied locally to support joint comfort (3-12). In aromatherapy, eucalyptus oil is used to enhance creative mental concentration, calm anxiety, and ease discomfort through its cooling properties (9).

Global Recognition of Eucalyptus

Eucalyptus oil is officially recognized in the Chinese Pharmacopoeia. The Indian Pharmacopoeia lists it as a counterirritant and mild expectorant, while the Ayurvedic Pharmacopoeia indicates its topical application for supported mental clarity  (3-5).

Eucalyptus oil is traditionally applied locally to support the opening of the nasal passages (3-5). It can also help combat several strains of Streptococcus (3-12).

Scientific Study of Eucalyptus’s Medicinal Properties

Eucalyptus oil has been well-studied in human clinical trials. For example, a leaf extract of Eucalyptus globulus was shown to be effective against different types of bacteria, including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, and Haemophilus influenzae, obtained from 200 clinical specimens of patients with respiratory tract disorders (7). A prospective randomized, double-blind, controlled trial of five aromatic essential oils including Eucalyptus globulus in patients with upper respiratory tract infections showed that all five aromatic plants brought about significant and immediate improvement (8).

A clinical trial in Korea studied the effects of inhaled eucalyptus oil dissolved in almond oil on the inflammatory response after total knee replacement. The results showed the oil improved patients’ subjective pain scores when compared with the control group (9). A more recent review suggests eucalyptus oil is beneficial for chronic upper respiratory conditions (10).

The Chemistry of Eucalyptus Oil: Eucalyptol as a Powerful Monoterpene

Eucalyptus oil rectified by distillation has a characteristic chromatographic profile, which is analyzed by gas chromatography (11). More than 70 percent of the oil is comprised of a chemical called eucalyptol, or 1,8-cineole (11). Eucalyptol is a powerful yet safe monoterpene known for dissolving mucous and calming the respiratory tract and is proven to have clinical efficacy (6).

Eucalyptol soothes the upper respiratory tract by acting directly and indirectly on the airways. Its effects are twofold. First, it alleviates the cascade causing irritation; then, it acts on the body’s mediators (10).

Eucalyptol is also a flavoring agent  approved by the Flavor and Extract Manufacturers Association of the United States (FEMA) and the Food and Drug Administration for use in foods (6). The compound is widely used as fragrance component in cosmetics, with maximum use levels of 1.6 percent in perfumes (6).

The Takeaway

Eucalyptus oil is a trusted ingredient that preserves the traditional benefits of eucalyptus leaves but provides more consistent effects. Its soothing properties can be attributed to its high eucalyptol content (10, 11). Eucalyptus essential oil is naturally uplifting and can soothe the upper respiratory tract while provide a cooling sensation on the throat and chest. 

References

  1. Information about Australia’s Flora, Aboriginal Plant Use in SE Australia, Australian National Botanic Gardens, consulted at: https://anbg.gov.au/aborig.s.e.aust/eucalyptus-species.html
  2. Eucalyptus globulus in: Bugwood Wiki, High Plains IPM website available at: https://wiki.bugwood.org/Eucalyptus_globulus
  3. Blumenthal M. Busse WR Goldberg A, Gruenwald J, Hall T, Klein, Riggins CW, Rister RS. (Eds) Eucalyptus oil, Eucalypti aetheroleum Eucalyptus In: The Commission E Monographs, American Botanical Council, Austin, TX, Published September 24, 1986; Revised March 13, 1990,
  4. Blumenthal, M. Goldberg A. and Brinkmann J. (Eds) Eucalyptus oil, Herbal Medicine: Expanded Commission E Monographs, American Botanical Council, Published by Integrative Medicine Communications, Newton NJ, 2003,
  5. Aetheroleum Eucalypti WHO Monographs on Selected Medicinal Plants. Vol 2. Geneva, Switzerland: World Health Organization; 2002.
  6. Khan IA, Abourashed EA. Leung’s Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. Third edition, John Wiley & Sons, Inc., New York, 2010.
  7. Salari MH, Amine G, Shirazi MH, Hafezi R, Mohammadypour M. Antibacterial effects of Eucalyptus globulus leaf extract on pathogenic bacteria isolated from specimens of patients with respiratory tract disorders. Clin Microbiol Infect. 2006; 12(2):194-6.
  8. Ben-Arye E, Dudai N, Eini A, Torem M, Schiff E, Rakover Y. Treatment of upper respiratory tract infections in primary care: a randomized study using aromatic herbs Evid Based Complement Alternat Med. 2011; 2011:690346.
  9. Jun YS, Kang P, Min SS, Lee J-M, Kim H-K, Seol GH. Effect of eucalyptus oil inhalation on pain and inflammatory responses after total knee replacement: A randomized clinical trial. Evid Based Complement Alternat Med. 2013; 2013:502727.
  10. Juergens UR, Anti-inflammatory properties of the monoterpene 1.8-cineole: current evidence for co-medication in inflammatory airway diseases. Drug Res (Stuttg). 2014;64(12):638-46. doi: 10.1055/s-0034-1372609.
  11. ISO 770 Crude or rectified oils of Eucalyptus globulus (Eucalyptus globulus) Eucalyptus oil, 2002, Technical Committee ISO/TC 54, Essential oils, International Standards Organization, Geneva, Switzerland.
  12. Community herbal monograph on Eucalyptus globulus Labill., Eucalyptus polybractea R.T. Baker and/or Eucalyptus smithii R.T. Baker, aetheroleum EMA/HMPC/307781/2012