Many generations of children remember the strong, aromatic smell of eucalyptus. Our mothers were quick to bring out the family supply of whatever eucalyptus product was available at the time and liberally slather it on our chests when we were in the throes of a bad cold or had the croup or bronchitis.

While Mom may not have understood the chemical activity that helped us to breathe easier, the relief that eucalyptus provided was enough to continue the practice. Today, there are multiple brand-name products that contain eucalyptus oil for medicinal uses.

Background

Australia is the world’s main producer of eucalyptus oil.1 Also called the “gum tree,” eucalyptus is an evergreen, and its leaves are broad, whitish-green, and waxy. It is the leaves of Eucalyptus globulus that are harvested for the distillation of its essential oil. The active ingredient of eucalyptus oil is 1.8-cineol, or eucalyptol.2  

Science

The actual mechanism of action in eucalyptus oil is still unclear. Generally, eucalyptus oil is thought to be anti-inflammatory and antimicrobial. There is some evidence that it can be used as an antifungal agent.3  

One study examined the effect of eucalyptus oil on human monocytes, specifically its ability to stimulate protective macrophage activity.4 The substance was also studied for its effect on the release of pro-inflammatory cytokines. Eucalyptus oil significantly induced macrophage activation and reduced the release of inflammatory cytokines.4

Steroid-dependent asthma patients were studied to determine the potential for steroid reduction when treated with an oral preparation of eucalyptus oil.5 After randomization, patients’ daily steroid doses were reduced by 2.5 mg every three weeks. At the end of 12 weeks, 36% of the patients on the active eucalyptus-oil therapy tolerated an average of 3.5 mg/day reduction in oral steroid use while only 7% of the placebo-treated patients were able to decrease their daily dose with an average reduction of 0.91 mg/day.

Eucalyptus oil has also been studied for its potential as an antimicrobial. A study of 56 respiratory isolates from 200 symptomatic patients showed definite antimicrobial activity with eucalyptus oil.6 Isolates included Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, and Haemophilus influenzae. With the rise in antimicrobial resistance, a potential new method for treating these infections is welcome news.

A separate study examining the use of eucalyptus oil in asthmatic patients explored the extract’s effect on nitric oxide in respiratory cells.7 Previous studies have shown an increase in exhaled nitric oxide in cases of eosinophilic inflammation and other indices of asthma-related inflammation. If eucalyptus oil is found to mitigate inflammation in such patients, this could lead to significant nonsteroidal treatment options for asthma. This trial showed that the extract was highly effective at inhibiting the induction of nitric oxide and the concomitant pro-inflammatory effects, further suggesting that eucalyptus extract may be a clinically viable option for asthmatic patients.

E. globulus has also been tested to determine its analgesic and anti-inflammatory effects in rat models.8 Eucalyptus-oil extract induced analgesic effects in this animal cohort, and was designed to show both peripheral and central pain relief. Another arm of the same trial measured—and confirmed—the anti-inflammatory benefits of eucalyptus oil.

Safety, interactions

Eucalyptus oil is unsafe when taken by mouth or applied directly to the skin without being diluted.3 Fatal allergic reactions have occurred with ingestion of eucalyptus products. Even though eucalyptus use in asthma and bronchitis has been shown to be beneficial, bronchospasm can result with inhalation.3

Eucalyptus oil is not recommended for use in pregnant or nursing women or in infants. If using a topical formulation for the first time, a patch test is recommended. This involves applying the extract to the upper arm. If no rash occurs after 24 hours, it is typically safe to proceed. Clinicians considering the use of diluted oral eucalyptus should proceed with caution. There is little data regarding drug interactions.

How supplied, dosage

There is no standardization for the dosing of eucalyptus oil. The literature states that for the oil to be medicinally effective, it must contain at least 70% to 85% of 1.8-cineol.9 Eucalyptus extract is supplied in multiple formulations, most for topical or inhaled use.

Summary

Developing research suggests that a chemical in eucalyptus may be able to break up mucus in persons with severe asthma, thus allowing for lowered steroid maintenance in such patients.3 But overall research to date ­suggests that more evidence is needed to rate the effectiveness of eucalyptus as complementary therapy.

Sherril Sego, FNP-C, DNP, is a staff clinician at the VA Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.

References

  1. Centre for Plant Biodiversity Research: The history of Eucalyptus page. Euclid website.
  2. University of Maryland Medical Center. Eucalyptus.
  3. MedlinePlus. Eucalyptus.
  4. Serafino A, Sinibaldi Vallebona P, Andreola F, et al. Stimulatory effect of Eucalyptus essential oil on innate cell-mediated immune response. BMC Immunol. 2008; 9:17.
  5. Juergens UR, Dethlefsen U, Steincamp G, et al. Anti-inflammatory activity of 1.8-cineol (eucalyptol) in bronchial asthma: a double-blind placebo-controlled trial. Respir Med. 2003;97:250-256.
  6. Salari MH, Amine G, Shirazi MH, et al. Antibacterial effects of Eucalyptus globulus leaf extract on pathogenic bacteria isolated from specimens of patients with respiratory tract disorders. Clin Microbiol Infect. 2006;12:194-196.
  7. Vigo E, Cepeda A, Gualillo O. Perez-Fernandez R. In-vitro anti-inflammatory effect of Eucalyptus globulus and Thymus vulgaris: nitric oxide inhibition in J774A.1 murine macrophages. J Pharm Pharmacol. 2004;56:257-263.
  8. Silva J, Abebe W, Sousa SM, et al. Analgesic and anti-inflammatory effects of essential oils of Eucalyptus.
  9. Sartorelli P, Marquioreto AD, Amarol-Baroli A, et al. Chemical composition and antimicrobial activity of the essential oils from two species of Eucalyptus. Phytother Res. 2007;21:231-233.

All electronic documents accessed October 15, 2012.