Active constituents
The major constituent in eucalyptus leaves is a volatile oil known as eucalyptol
(1,8-cineol). In order to provide an effective expectorant and antiseptic action, the leaf oil
should contain approximately 70–85% eucalyptol.3 Eucalyptus oil is said to
function in a fashion similar to that of
menthol by acting on receptors in the nasal mucosa, leading to a reduction in symptoms
such as nasal congestion.4 In test
tube studies, eucalyptus species have been shown to possess antibacterial actions against such
organisms as Bacillus subtilis,5 as well as several strains of
Streptococcus.6 These actions have not been researched in human clinical
trials.
Peppermint (10 grams) and eucalyptus oil (5
grams) in combination, applied topically to the forehead and temples for three minutes with a
small sponge, have been shown to be helpful as a muscle relaxant (but not for pain relief) in
people with tension headaches.7 A eucalyptus oil extract containing 50%
p-methane-3,8-diol (PMD) as the active ingredient has been shown to be effective in protecting
human volunteers from various types of biting insects.8 On human forearms, it was
determined that the eucalyptus extract was nearly as effective as a 20% solution of
diethyltoluamine (used in many insect repellents) in repelling bites of the Anopheles
mosquito (the insect that spreads malaria) for up to five hours. The eucalyptus extract was
also effective at repelling flies (94%) and midges (100%) for up to six hours.
A preliminary study suggests the combination of eucalyptus and menthol as a nasal inhalant is helpful in cases of
mild to moderate snoring.9 Also, in a double-blind trial, a eucalyptus-based rub
was found helpful for warming muscles in athletes.10 This further suggests
eucalyptus may help relieve minor muscle soreness when applied topically, though studies are
needed to confirm this possibility.
Are there any side effects or interactions?
Side effects from the internal use of eucalyptus can include nausea, vomiting, and diarrhea. Eucalyptus oil should not be used by infants
and children under the age of two, especially near the face and nose, due to the risk of
airway spasm and possible cessation of breathing.13 The oil may aggravate bronchial
spasms in people with asthma and should not be
taken internally by those with severe liver diseases and inflammatory disorders of the
gastrointestinal tract and kidney.14 15 Whole-body application of
eucalyptus oil (double-distilled, containing 80–85% cineole oil) resulted in severe
nervous system toxicity in a six year old girl.16 Parents are advised to use
topical eucalyptus oil in moderation with children.
Although there are no known reports of drug interactions, the German Commission E monograph
suggests that because eucalyptus oil may activate certain enzyme systems in the liver, it may
potentially weaken or shorten the action of some medications, including pentobarbital,
aminopyrine, and amphetamine.17 18 Eucalyptus should not be used in
large amounts by people with low blood pressure as it may cause a further drop in blood
pressure.19 The safety of eucalyptus oil has not been established in pregnant or nursing women.
At the time of writing, there were no well-known drug interactions
with eucalyptus.
1. Wren RC. Potter’s New Cyclopedia of Botanical Drugs and
Preparations. Essex, England: C.W. Daniel Co., 1988, 110–1.
2. Castleman M. The Healing Herbs. Emmaus, PA: Rodale Press,
1991, 162–3.
3. Robbers JE, Tyler VE. Tyler’s Herbs of Choice: The
Therapeutic Use of Phytomedicines. New York: Haworth Press, 1999, 123.
4. Schulz V, Hansel R, Tyler VE. Rational Phytotherapy, 3rd ed.
Berlin, Germany: Springer-Verlag, 1998, 146–7.
5. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients
Used in Food, Drugs, and Cosmetics, 2d ed. New York: John Wiley & Sons, 1996,
232–3.
6. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide
for Health-Care Professionals. London: The Pharmaceutical Press, 1996, 108.
7. Gobel H, Schmidt G, Dowarski M, et al. Essential plant oils and
headache mechanisms. Phytomed 1995;2:93–102.
8. Trigg JK, Hill N. Laboratory evaluation of a eucalyptus-based insect
repellent against four biting arthropods. Phytother Res 1996;10:313–6. Reviewed
by Yarnell E. Selected herbal research summaries QRNM 1997;116.
9. Ishizuka Y, Imamura Y, Tereshima K, et al. Effects of nasal inhalation
capsule. Oto-Rhino-Laryngology Tokyo 1997;40:9–13.
10. Hong CZ, Shellock FG. Effects of a topically applied counter irritant
(Eucalyptamint) on cutaneous blood flow and on skin and muscle temperature: A placebo
controlled study. Am J Phys Med Rehab 1991;70:29–33.
11. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide
for Health-Care Professionals. London: The Pharmaceutical Press, 1996, 108.
12. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients
Used in Food, Drugs, and Cosmetics, 2d ed. New York: John Wiley & Sons, 1996,
232–3.
13. Schulz V, Hansel R, Tyler VE. Rational Phytotherapy, 3rd ed.
Berlin, Germany: Springer-Verlag, 1998, 146–7.
14. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete
German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin: American
Botanical Council and Boston: Integrative Medicine Communications, 1998, 127–8.
15. Brinker F. Herb Contraindications and Drug Interactions.
Sandy, OR: Eclectic Institute Publishers, 1997, 46–7.
16. Darben T, Cominos B, Lee CT. Topical eucalyptus oil poisoning.
Australas J Dermatol 1998;39:265–7.
17. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete
German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin: American
Botanical Council and Boston: Integrative Medicine Communications, 1998, 127–8.
18. Brinker F. Herb Contraindications and Drug Interactions.
Sandy, OR: Eclectic Institute Publishers, 1997, 46–7.
19. Brinker F. Herb Contraindications and Drug Interactions.
Sandy, OR: Eclectic Institute Publishers, 1997, 46–7.