Eucalyptus: nature's aromatic decongestant: eucalyptus trees are tall evergreens native to Australia. But, today, you'll find these majestic giants growing worldwide, including the Mediterranean regions, southern California, and South America. There are about 700 species, but only two dozen--found mostly in Australia. Spain, and Morocco--are used to produce eucalyptus oil.

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One eucalyptus tree--the Mountain Ash--is among the tallest in the world, towering almost 300 feet above the forest floor.

Eucalyptus belongs to the myrtle family; the same clan that includes guava, all-spice, cloves, and Melaleuca. The eucalyptus flowers are dressed in white, cream, pink, or red; and their nectar produces a high-quality honey. This nectar is a popular food for many native Australian birds, bats, and possums.

The cone-shaped, woody fruits, known as gum nuts, are commonly used in floral decorations, and the leaves often find a welcome place in potpourris and linen sachets.

Economic Use

Since they are among the fastest-growing plants in the world, eucalyptus trees have proven to be very useful. Their rapid growth rates make them an effective windbreak for farms and highways. They're also valuable for timber, firewood, and shade. Because they draw a large volume of water from the ground, eucalyptus trees effectively lower water tables and help drain swampy areas.

Many species are grown as ornamentals in cities and gardens because of their handsome foliage and patterned bark. The Australian Aborigines use the wood to make a musical wind instrument known as a "didgeridoo."

Eucalyptus leaves are covered with oil glands. This volatile oil is obtained by steam distillation of fresh leaves or from the tips of branches. Dried, mature leaves from the older trees can also be used.

Some of these oils find a home in perfumery and detergents and are an active ingredient in insect repellents. Others help remove oily or greasy spots on clothing.

Traditional Use

Eucalyptus leaves treated fevers and other health conditions in traditional Australian Aboriginal medicine. Aborigines also use bark decoctions to bathe sores and water solutions of the oleoresin for inflammations of the bladder. Even today, topical applications of eucalyptus treat sprains and wounds.

The oil is believed to possess antispasmodic properties and has been used therapeutically not only in Australia, but in Chinese, European, and Indian traditional medicine as well.

Therapeutic Use

Eucalyptus is a champion aromatic herb used for the temporary relief of nasal and pulmonary congestion. It's a frequent component in modern decongestant formulations and commonly serves as a mild expectorant in cough drops and lozenges, cough mixtures, and cold medications.

Eucalyptus assists breathing by opening the nasal passages and sinuses, and often appears as a component of over-the-counter products for the treatment of sinusitis and pharyngitis. The vapor of a hot herbal infusion can be deeply inhaled.

The leaves of eucalyptus contain tannins, phenolic acids, terpenoids, and flavonoids. The flavonoids possess antioxidant and anti-inflammatory properties.

Eucalyptus is useful as a medicinal tea to treat bronchial and other respiratory problems, as well as inflammation of the mouth and throat. One-half teaspoon of crushed leaves can be used to make a tea, which can be consumed two to three times a day.

It's also considered an antibacterial agent. Cineole, or eucalyptol, makes up about 70 to 80 percent of the essential oil of eucalyptus. Cineole generates antimicrobial effects and demonstrates activity against many bacteria such as candida, staphylococcus, and streptococcus. The oil is useful as a disinfectant and antiseptic. It contains citronellal, providing a lemon-like scent.

Warning: Not for Internal Use

Eucalyptus oil should be kept clear of mucous membranes, as it may cause hypersensitivity reactions. The oil can be toxic when taken internally. Ingestion may alter the effectiveness of oral agents in the treatment of diabetes, and affect blood-sugar levels. Pregnant women and infants should not ingest the oil for any reason at any time.

Toxic amounts produce nausea, vomiting, and diarrhea. Poisoning may occur with only 4 to 5 cc's of the oil, causing a drop in blood pressure and circulation problems. Preparations of eucalyptus leaves should not be given in cases of inflammation of the gastrointestinal tract or for serious liver complaints.

However, when used externally, eucalyptus provides effective therapy for the treatment of bronchitis and upper respiratory conditions, nasal congestion, mouth and throat infections, coughs, and cold symptoms. Its decongestant and anti-inflammatory properties are well known.

Winston J. Craig, Ph.D., R.D., is professor of nutrition at Andrews University, Berrien Springs, Michigan.