Tea Tree Oil
The medicinal benefits and safety considerations you should know.
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Tea tree oil is made by the steam distillation of the leaves of the tea tree (scientific name: Melaleuca alternifolia from the Myrtaceae family). Tea tree oil is a natural remedy with a long history of traditional use among Aboriginal peoples of Australia as an antiseptic and herbal medicine for various external applications. Tea tree oil is now used across the world in topical treatments of various dermatologic conditions such as acne, athlete’s foot, lice, nail fungus, cuts, and insect stings.
Tea tree oil contains hundreds of plant secondary metabolites (plant signaling and defense molecules). To ensure the quality of manufactured tea tree oil, the International Organization for Standardization has established minimum and maximum concentrations for 15 of these components. The primary active constituent, terpinen-4-ol, makes up between 35%–48% of tea tree oil.
Clinical Findings
A systematic review of 46 human clinical trials spanning the fields of dentistry, dermatology, infectious disease, ophthalmology, and podiatry. I’ve summarized some of the major findings below:
Oral Health and Hygiene
A number of studies have investigated the utility of tea tree oil in reducing dental plaque and treating gingivitis:
Twelve clinical trials have tested the efficacy of tea tree oil for controlling microbial plaque on tooth surfaces.
Tea tree oil-based mouthwashes have shown effectiveness in reducing dental plaque, gingival inflammation, and salivary microbes.
Studies in children aged 8-15 years demonstrated significant reductions in dental plaque, gingival inflammation, and the bacteria Streptococcus mutans count with tea tree oil mouthwash.
In adults, tea tree oil mouthwashes were found to be effective in reducing dental plaque and gingival inflammation, with some studies reporting adverse effects like burning sensation and altered taste perception.
Gingivitis: One study indicated that tea tree oil mouthwash was more effective than chlorhexidine in reducing gingival inflammation.
Dermatology
Topical (external) applications of tea tree oil are among the most common applications and these align with many of the traditional medical practices associated with this plant.
Acne Vulgaris: Three trials demonstrated that tea tree oil-based gels (5%-6%) significantly reduce acne lesion counts and severity in subjects with mild to moderate acne. Compared to benzoyl peroxide, tea tree oil caused fewer adverse effects like dryness and stinging.
Wound Healing: Tea tree oil was tested for burn wound treatment and skin perfusion. It showed increased blood flow in a saline solution but was less effective than running tap water for reducing skin surface temperature in burns.
Seborrheic Dermatitis: A 5% tea tree oil gel significantly reduced clinical signs like erythema, scaling, itching, and greasy crusts compared to a placebo.
Skin Inflammation: Tea tree oil added to a cooling ointment showed increased skin erythema in non-irradiated skin, indicating mild irritation, but did not significantly differ in reducing inflammation compared to other treatments.
Dandruff: A 5% tea tree oil shampoo was significantly more effective in reducing the area and severity of dandruff compared to a placebo. Mild adverse effects such as stinging, burning, and itching were reported by a few subjects.
Infectious Disease
The antiseptic properties of tea tree oil have been well-studied and represent an important aspect of traditional use of the oil.
MRSA Infection: Four trials tested tea tree oil-based products for MRSA prevention and eradication, showing mixed results. Tea tree oil was as effective as standard treatments in some cases, but less effective for nasal decolonization compared to Bactroban®.
Hand Disinfection: Three trials found that tea tree oil-based hand disinfectants and soaps significantly reduced microbial counts on hands, often outperforming standard alcohol-based and benzalkonium chloride-based sanitizers.
Molluscum Contagiosum: A trial comparing tea tree oil combined with iodine to tea tree oil or iodine alone found the combination significantly more effective in resolving lesions. Minor adverse effects like redness and warmth were reported.
Oral Candida Infection: A study comparing a 0.25% tea tree oil mouthwash to clotrimazole ointment and standard care showed larger reductions in signs of infection with tea tree oil and clotrimazole, though no statistical comparisons were made.
General Safety: Across various trials, tea tree oil was generally well-tolerated with minimal adverse effects, such as mild skin irritation and nasal mucosa swelling.
Safety Considerations
Tea tree oil should never be ingested, as oral consumption can lead to severe symptoms including confusion, ataxia (loss of muscle coordination), breathing difficulties, and coma. While most individuals can safely use topical products containing tea tree oil, some may experience contact dermatitis (an allergic skin rash) or skin irritation in areas where the product is applied. Additionally, there is limited information on the safety of using tea tree oil during pregnancy or while breastfeeding, so caution is advised.
The Takeaway
Tea tree oil is the steam-distilled essential oil product of the Australian plant, Melaleuca alternifolia. The major component of the oil is the bioactive molecule terpinen-4-ol. Many laboratory and clinical studies have been performed on tea tree oil and efficacy has been established in a number of fields, ranging from dermatology, oral health, and infection control. Like anything from nature, tea tree oil is not completely safe. It should never be ingested and any use in oral hygiene should be undertaken with care not to swallow the oil. Topical uses are generally well-tolerated, but tea tree oil can cause allergic contact dermatitis. As with any essential oil, the safest way to use it is diluted in a base liquid such as water or a plant-based oil.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a Guggenheim Fellow, Fellow of the National Academy of Inventors, and award-winning author of The Plant Hunter. Her day job is as professor and herbarium curator at Emory University School of Medicine, where she leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription.
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