Melaleuca alternifolia, commonly known as tea tree (not used to make tea. The tea is made from Camellia sinensis), is a small tree or shrub native to Australia, specifically to swampy areas of the northeastern coast of New South Wales. The plant is renowned for its essential oil, which is extracted from its leaves and is widely acclaimed for its antiseptic and antibacterial properties.

Botanical Classification

Kingdom: Plantae
Clade: Angiosperms
Class: Eudicots
Order: Myrtales
Family: Myrtaceae
Genus: Melaleuca
Species: M. alternifolia

Plant Characteristics

Melaleuca alternifolia typically grows to about 5 to 7 meters tall. The tree has a bushy appearance with whitish, papery bark and needle-like leaves that are alternately arranged, giving the plant its name. The leaves are rich in oil glands, visible as tiny dots. It produces small, fluffy, white to cream-colored flowers in spikes or heads, which bloom in the late spring or early summer.

Chemical Composition and Structure

The leaves of Melaleuca alternifolia contain a potent essential oil, predominantly made up of terpinen-4-ol, which is responsible for most of its antimicrobial activities. Other components include cineole, pinene, and terpinenes. These compounds collectively contribute to the oil's strong antiseptic, antifungal, and insecticidal properties.

How to Cultivate It

To successfully cultivate Melaleuca alternifolia:

1. Soil: Prefers well-drained, sandy soils but can tolerate a range of soil types, including clay.
2. Light: Thrives in full sun.
3. Water: Requires moderate watering, with more frequent irrigation needed in dry conditions. The plant is somewhat drought-resistant once established.
4. Temperature: Hardy in various climates but does not tolerate frost well. It is best suited to warm, temperate regions.

Uses and Benefits

Tea tree oil is extensively used in dermatology and for medicinal purposes to treat a variety of skin conditions, including acne, fungal infections, and dandruff. It is also used as a natural remedy for lice, scabies, and athlete’s foot. Due to its soothing properties, it is commonly found in creams, ointments, and shampoos.

Applications

• Medicinal: The oil is used topically for its healing properties and is a staple in alternative medicine for treating minor wounds and infections.
• Cosmetic: Incorporated into skincare and hair care products for its antiseptic qualities.

INCI Functions:

Skin conditioning agent. It is the mainstay of topical skin treatment as it has the function of restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants that can be added in the formulation.

• Household: Used in cleaning products for its ability to kill bacteria and mold without the use of harsh chemicals.

Environmental and Safety Considerations

Melaleuca alternifolia is considered an environmentally friendly plant. 

It is important, however, to ensure sustainable harvesting of the leaves to maintain healthy populations. 

While tea tree oil is generally safe for topical use, it should never be ingested as it can be toxic. Always dilute the essential oil with a carrier oil before application to the skin to minimize the risk of irritation.

References__________________________________________________________________________

Carson CF, Hammer KA, Riley TV. Melaleuca alternifolia (Tea Tree) oil: a review of antimicrobial and other medicinal properties. Clin Microbiol Rev. 2006 Jan;19(1):50-62. doi: 10.1128/CMR.19.1.50-62.2006.

Abstract. Complementary and alternative medicines such as tea tree (melaleuca) oil have become increasingly popular in recent decades. This essential oil has been used for almost 100 years in Australia but is now available worldwide both as neat oil and as an active component in an array of products. The primary uses of tea tree oil have historically capitalized on the antiseptic and anti-inflammatory actions of the oil. This review summarizes recent developments in our understanding of the antimicrobial and anti-inflammatory activities of the oil and its components, as well as clinical efficacy. Specific mechanisms of antimicrobial and anti-inflammatory action are reviewed, and the toxicity of the oil is briefly discussed.

Lam NSK, Long XX, Griffin RC, Chen MK, Doery JC. Can the tea tree oil (Australian native plant: Melaleuca alternifolia Cheel) be an alternative treatment for human demodicosis on skin? Parasitology. 2018 Oct;145(12):1510-1520. doi: 10.1017/S0031182018000495. 

Abstract. Australian tea tree oil (TTO) and its extract terpinen-4-ol (T4O) are found to be effective in moderating demodex-related diseases. Their possible effects are lowering the mite counts, relieving the demodex-related symptoms and modulating the immune system especially the inflammatory response. This review summarizes the topical treatments of TTO and T4O in human demodicosis, their possible mechanism of actions, side-effects and potential resistance in treating this condition. Although current treatments other than TTO and T4O are relatively effective in controlling the demodex mite population and the related symptoms, more research on the efficacy and drug delivery technology is needed in order to assess its potential as an alternative treatment with minimal side-effect profile, low toxicity and low risk of demodex resistance.

Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006–. Tea Tree Oil. 2023 Apr 15.

Abstract. Tea tree (Melaleuca alternifolia) oil contains primarily terpinen-4-ol, but more than 100 other constituents have been identified, including 1,8-cineole (eucalyptol). Tea tree oil should not be confused with cajeput oil, niauouli oil, kanuka oil, or manuka oil which are obtained from other Melaleuca species. Other than eucalyptol, no data exist on the excretion of components of tea tree oil into breastmilk or on the safety and efficacy of tea tree oil in nursing mothers or infants. Topical tea tree oil is generally well tolerated, but should not be taken orally. Tea tree oil is usually used topically for the treatment of infections and has been used for prophylactic treatment of the nipples postpartum.[1] However, tea tree oil has estrogenic and antiandrogenic activity and numerous cases of breast enlargement in boys have been reported.[2-5] The relevance of these findings has been questioned,[6-9] but no further testing has been reported to confirm or refute the findings. Topical application around the breast should be avoided unless it is thoroughly removed before nursing. Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.

Hammer KA, Carson CF, Riley TV, Nielsen JB. A review of the toxicity of Melaleuca alternifolia (tea tree) oil. Food Chem Toxicol. 2006 May;44(5):616-25. doi: 10.1016/j.fct.2005.09.001. 

Abstract. The essential oil of Melaleuca alternifolia, also known as tea tree or melaleuca oil, is widely available and has been investigated as an alternative antimicrobial, anti-inflammatory and anti-cancer agent. While these properties are increasingly well characterised, relatively limited data are available on the safety and toxicity of the oil. Anecdotal evidence from almost 80 years of use suggests that the topical use of the oil is relatively safe, and that adverse events are minor, self-limiting and occasional. Published data indicate that TTO is toxic if ingested in higher doses and can also cause skin irritation at higher concentrations. Allergic reactions to TTO occur in predisposed individuals and may be due to the various oxidation products that are formed by exposure of the oil to light and/or air. Adverse reactions may be minimised by avoiding ingestion, applying only diluted oil topically and using oil that has been stored correctly. Data from individual components suggest that TTO has the potential to be developmentally toxic if ingested at higher doses, however, TTO and its components are not genotoxic. The limited ecotoxicity data available indicate that TTO is toxic to some insect species but more studies are required.

Crawford GH, Sciacca JR, James WD. Tea tree oil: cutaneous effects of the extracted oil of Melaleuca alternifolia. Dermatitis. 2004 Jun;15(2):59-66. doi: 10.2310/6620.2004.04003. 

Abstract. The use of botanical extracts for their perceived therapeutic benefits has gained increased popularity in this country and abroad. In particular, tea tree oil (the extracted oil of Melaleuca alternifolia) has gained widespread use for its purported antimicrobial and therapeutic effects. In parallel with this increased use is an expanding series of reported adverse effects, including allergic contact dermatitis, systemic contact dermatitis, linear immunoglobulin A disease, erythema multiforme-like id reactions, and systemic hypersensitivity reactions. We present a review of tea tree oil with regard to its history, chemistry, purported medicinal uses, and possible adverse cutaneous effects.