Eucalyptus is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. The fruit is a woody capsule commonly referred to as a “gumnut”.
Most species of Eucalyptus are native to Australia, a few species are native to islands north of Australia. A smaller number are only found outside the continent. Eucalypts have been grown in plantations in many other countries because they are fast-growing and have valuable timber, or can be used for pulpwood, for honey production or essential oils. In some countries, however, they have been removed because they are highly flammable.
In continental Portugal, the Azores and continental Spain (especially in Cantabria, Biscay, Asturias and Galicia in the north, and Huelva in Andalusia) farmland has been replaced with eucalypt plantations since their introduction by Rosendo Salvado in the 19th century.
In Italy, the eucalyptus only arrived at the turn of the 19th century and large scale plantations were started at the beginning of the 20th century with the aim of drying up swampy ground to defeat malaria. During the 1930s, Benito Mussolini had thousands of eucalyptus plants planted in the marshes around Rome. This, their rapid growth in the Italian climate and excellent function as windbreaks, has made them a common sight in the south of the country, including the islands of Sardinia and Sicily. They are also valued for the characteristic smelling and tasting honey that is produced from them. The variety of eucalyptus most commonly found in Italy is E. camaldulensis.
In Greece, eucalypts are widely found, especially in southern Greece and Crete. They are cultivated and used for various purposes, including as an ingredient in pharmaceutical products (e.g., creams, elixirs and sprays) and for leather production. They were imported in 1862 by botanist Theodoros Georgios Orphanides. The principal species is Eucalyptus globulus.
Eucalyptus has been grown in Ireland since trials in the 1930s and now grows wild in South Western Ireland in the mild climate.
Size and habit
Eucalypts vary in size and habit from shrubs to tall trees. Trees usually have a single main stem or trunk but many eucalypts are mallees that are multistemmed from ground level and rarely taller than 10 metres (33 feet).
Tree sizes follow the convention of:
- Small: to 10 m (33 ft) in height
- Medium-sized: 10–30 m (33–98 ft)
- Tall: 30–60 m (98–197 ft)
- Very tall: over 60 m (200 ft)
Eucalyptus oil is readily steam distilled from the leaves and can be used for cleaning and as an industrial solvent, as an antiseptic, for deodorising, and in very small quantities in food supplements, especially sweets, cough drops, toothpaste and decongestants. It has insect-repellent properties and serves as an active ingredient in some commercial mosquito-repellents.
Aromatherapists have adopted eucalyptus oils for a wide range of purposes.
Eucalyptus globulus is the principal source of eucalyptus oil worldwide.
Eucalyptus oil is the generic name for distilled oil from the leaf of Eucalyptus, a genus of the plant family Myrtaceae native to Australia and cultivated worldwide. Eucalyptus oil has a history of wide application, as a pharmaceutical, antiseptic, repellent, flavouring, fragrance and industrial uses. The leaves of selected Eucalyptus species are steam distilled to extract eucalyptus oil.
As an ingredient
The cineole-based oil is used as a component in pharmaceutical preparations to relieve the symptoms of influenza and colds, in products like cough sweets, lozenges, ointments and inhalants. Inhaled eucalyptus oil vapour may be a decongestant. The main chemical components of eucalyptus oil, eucalyptol and alpha-terpineol, give the oil a soothing, cooling vapour. This makes eucalyptus oil useful for massage. Eucalyptus oil is used in personal hygiene products in dental care.
Repellent and biopesticide
Cineole-based eucalyptus oil is used as an insect repellent and biopesticide. In the U.S., eucalyptus oil was first registered in 1948 as an insecticide and miticide.
Flavouring and fragrance
Eucalyptus oil is used in flavouring. Cineole-based eucalyptus oil is used as a flavouring at low levels (0.002%) in various products, including baked goods, confectionery, meat products and beverages. Eucalyptus oil has antimicrobial activity against a broad range of foodborne human pathogens and food spoilage microorganisms. Non-cineole peppermint gum, strawberry gum and lemon ironbark are also used as a flavouring. Eucalyptus oil is also used as a fragrance component to impart a fresh and clean aroma in soaps, detergents, lotions, and perfumes. It is known for its pungent, intoxicating scent. Due to its cleansing properties, Eucalyptus oil is found in mouth rinses to freshen breath.
Research shows that cineole-based eucalyptus oil (5% of mixture) prevents the separation problem with ethanol and petrol fuel blends. Eucalyptus oil also has a respectable octane rating and can be used as a fuel in its own right. However, production costs are currently too high for the oil to be economically viable as a fuel.
Phellandrene- and piperine-based eucalyptus oils have been used in mining to separate sulfide minerals via flotation.
Eucalyptus oil has natural anti-microbial and antiseptic properties and is used in household cleaning applications. It is commonly used in commercial laundry products such as wool wash liquid. It is used as a solvent for removing grease and sticky residue.
Safety and toxicity
If consumed internally at a low dosage as a flavouring component or in pharmaceutical products at the recommended rate, cineole-based ‘oil of eucalyptus’ is safe for adults. However, systemic toxicity can result from ingestion or topical application at higher than recommended doses. In Australia, eucalyptus oil is one of the many essential oils that have been increasingly causing cases of poisoning, mostly of children. In the period 2014-2018, there were 2049 reported cases in New South Wales, accounting for 46.4% of essential oil poisoning incidents.
The probable lethal dose of pure eucalyptus oil for an adult is in the range of 0.05 mL to 0.5 mL/per kg of body weight. Because of their high body-surface-area-to-mass ratio, children are more vulnerable to poisons absorbed transdermally. Severe poisoning has occurred in children after ingestion of 4 mL to 5 mL of eucalyptus oil.
Eucalyptus oil has also been shown to be dangerous to domestic cats, causing an unstable gait, excessive drooling, and other symptoms of ill health.
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