Eucalyptus

Encyclopedia of Alternative Medicine, Apr 06, 2001 by Jennifer Wurges

The eucalyptus tree is a large, fast-growing evergreen that is native to Australia and Tasmania. The tree can grow to 375-480 feet (125-160 meters). Eucalyptus belongs to the myrtle (Myrtaceae) family. There are over 300 species of eucalyptus, and Eucalyptus globulus is the most well-known species. One species (E. amygdalin) is the tallest tree known in the world. The tree grows best in areas with an average temperature of 60°F (15°C).

Eucalyptus trees constitute over 75% of the tree population of Australia. The eucalyptus tree is also known in Australia as the blue gum tree or malee. Other names for eucalyptus include Australian fever tree and stringy bark tree. The name is actually derived from the Greek word "eucalyptos," which means "well covered," and refers to the cuplike membrane that covers the budding flowers of the tree.

The bluish green leaves carry the medicinal properties of the tree and grow to a length of 6-12 inches (15-30 cm). While the leathery leaves are the sole food for koala bears, the leaves also contain a fragrant volatile oil that has antiseptic, expectorant, antibacterial, anti-inflammatory, deodorant, diuretic, and antispasmodic properties. Other constituents of the leaves include tannins, phenolic acids, flavonoids (eucalyptin, hyperin, hyperoside, quercitin, quercitrin, rutin), sesquiterpenes, aldehydes, and ketones.

Eucalyptus oil is obtained through a steam distillation process that removes the oil from the fresh, mature leaves and branch tips of older trees. Approximately 25 species of eucalyptus trees in Australia are grown for their oil.

There are three grades of eucalyptus oil: medicinal, which contains the compound eucalyptol (also called cineol); industrial, in which a component of the oil is used in mining operations; and aromatic, which is used in perfumes and fragrant soap products. These oils vary greatly in character. When choosing an oil for therapeutic use, it is important to know from what species the oil was derived. Species used medicinally include E. globulus, which contains up to 70% eucalyptol; E. polybractea, which contains 85% eucalyptol; and E. Smithii. Eucalpytus amygdalina and E. dives contain little eucalyptol and are used to separate metallic sulfides from ores in the mining industry. Eucalyptus citriodora contains a lemon-scented oil and is an ingredient in perfumes, as is E. odorata and E. Sturtiana. Two species, E. dives and E. radiata, have oils with a strong peppermint odor.

The most common species grown for its medicinal oil is Eucalyptus globulus. The eucalyptol found in this species is a chief ingredient in many over-the-counter cold and cough remedies, such as cough lozenges, chest rubs, and decongestants. It acts to stimulate blood flow and protects against infection and germs. The British Pharmocopoeia requires that commercial eucalyptus oils contain 55% eucalyptol by volume.

The Australian aborigines have used eucalyptus for hundreds of years as a remedy for fever, wounds, coughs, asthma, and joint pain. Australian settlers named the eucalyptus the fever tree because of its disease-fighting properties. Baron Ferdinand von Miller, a German botanist and explorer, was responsible for making the properties of eucalyptus known to the world in the mid-1800s. Likening eucalyptus' scent to that of cajaput oil (a disinfectant), von Miller suggested that eucalyptus might also be used as a disinfectant in fever districts. Seeds of the tree were sent to Algiers, France and planted. The trees thrived and, because of the drying action of the roots, turned one of the marshiest areas of Algiers into a dry and healthy environment, thereby driving away malaria-carrying mosquitoes. Eucalyptus trees were then planted in temperate areas around the world to prevent malaria. As a result, eucalyptus trees are now cultivated in China, India, Portugal, Spain, Egypt, South and North Africa, Algeria, South America, and in the southern portion of the United States.

Commercial production of eucalyptus began in Victoria, Australia in 1860. The nineteenth century eclectic doctors adopted eucalyptus as a treatment for fevers, laryngitis, asthma, chronic bronchitis, whooping cough , gonorrhea, ulcers, gangrenous tissue, edema, and gastrointestinal disturbances. European doctors used eucalyptus oil to sterilize their surgical and medical equipment. Eucalyptus leaves were often made into cigars or cigarettes and smoked to relieve asthma and bronchial congestion.

Modern medicines around the world have included eucalyptus in their practices. Indian ayurvedics use eucalyptus to treat headaches resulting from colds. Eucalyptus is listed in the Indian Pharmacopoeia as an expectorant and in the Chinese Pharmacopoeia as a skin irritant used in nerve pain. In France, eucalyptus leaves are applied topically to relieve congestion from colds and to treat acute bronchial disease. A standardized eucalyptus tea is licensed in Germany to treat bronchitis and throat inflammations. Eucalyptus is also an ingredient in German herbal cough preparations. The German Commission E has approved the internal use of eucalyptus to treat congestion of the respiratory tract, and the external use to treat rheumatic complaints. In the United States, eucalyptus is a component of many decongestant and expectorating cough and cold remedies, such as cough drops, cough syrups, and vapor baths. Eucalyptus is often used in veterinary medicine. It is used to treat horses with flu, dogs with distemper, and to treat parasitic skin conditions.