Melaleuca alternifolia.  Common tea tree, Narrow leafed tea tree   Family: Myrtaceae     
PART USED: Essential oil of foliage- Steam distilled
ACTIONS- External use only.
GROUP: Herbs Influencing Infection
1. Antiseptic.[3] Antifungal. Antipruritic. Astringent. Bacteriostatic.[3]
2. Respiratory decongestant.
3. Rubefacient.
4. Vulnerary. Tissue healing.
INDICATIONS- External use only.
1. Cuts, skin and nail infections, wounds and especially itching insect bites- can use neat (100%) or diluted to 15%.
2. Acne, cold sores, sores,[3]mouth ulcers, abscesses,[4]cuts,[4] abrasions,[4] boils.[4]- apply topically- often in creams or gel.
3. Flu and colds- steam inhalation. Can apply a few drops to handkerchief or pillow.
4. Athletes's foot (tinea), ringworm and other fungi-[4] add to a foot bath.
5. Vaginal infections- thrush- use diluted as douche. Gonorrhea- pussy discharge.[4]
6. Mouth ulcers., bleeding gums or oral thrush, following dental surgery or as a gargle for sore throats. Do not swallow.
7. Bacterial infections.- Streptococcus staphylococcus, thyphosus, diptheria, pneumococcus, gonococcus.
PRECAUTIONS: This oil may be irritating to sensitive skin. Avoid contact with eyes. External use only.
TOXIC: If poisoning occurs get to a doctor or hospital quickly. If swallowed to not induce vomiting. Give a glass of water.
PREPARATIONS:
Can be used neat on skin or diluted to 15% with ethanol and water.
Combined in creams and gels.
Steam inhalation.
Diluted as mouth wash.
This oil is a top note.

HABITAT: Usually in swampy or wet ground
ORIGIN: Northern coastal strip of New South Wales- from Port Macquarie northwards and southern Queensland.
DESCRIPTION: A shrub or small tree up to 5 m high with a papery bark. Its leaves are mostly alternate, very narrow (upto 1.5 mm), tapered at both ends and rarely exceeding 20 mm in length. Flowers occur in loose cream-colored spikes. Fruits are woody capsules, about 3 mm in diameter and occur in elongated clusters around branchlets. Flowers in summer. It may be distinguished from the very similar M. Linariifolia by its more compact habit, smaller overall size, narrower and shorter leaves as well as alternate leaf arrangement. Cushed foliage is aromatic.
References
Constituents
Monoterpenes, sesqueterpenes and their alcohols. Terpinen-4-ol is present at the highest levels, greater than 30% and possibly with g-terpinene, are responsible for most of the antimicrobial activity.[1]
The plants growing near the southern limits of the species' habitat, do not exhibit any of the bactericidal activity of the terpinen-4-ol rich form and may in fact act as an irritant if applied too often to the skin.[4]
References
[1] Medical and Dental Data of Ti-Trol and Melasol; Australian Essential Oils Ltd., Sydney, 1931, revised 1936
[2] A.R. Penfold and R.R. Morrison, Bulletin No. 14; Techmological Museum, Sydney, 1946
Cultivation, Harvesting and Supply
Research
Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties pdf
Effects of Melaleuca alternifolia (Tea Tree) Essential Oil and the Major Monoterpene Component Terpinen-4-ol on the Development of Single- and Multistep Antibiotic Resistance and Antimicrobial Susceptibility pdf

The mode of antimicrobial action of the essential oil of Melaleuca alternifolia (tea tree oil) pubmed.
S D Cox 1, C M Mann, J L Markham, H C Bell, J E Gustafson, J R Warmington, S G Wyllie
Abstract
The essential oil of Melaleuca alternifolia (tea tree) exhibits broad-spectrum antimicrobial activity. Its mode of action against the Gram-negative bacterium Escherichia coli AG100, the Gram-positive bacterium Staphylococcus aureus NCTC 8325, and the yeast Candida albicans has been investigated using a range of methods. We report that exposing these organisms to minimum inhibitory and minimum bactericidal/fungicidal concentrations of tea tree oil inhibited respiration and increased the permeability of bacterial cytoplasmic and yeast plasma membranes as indicated by uptake of propidium iodide. In the case of E. coli and Staph. aureus, tea tree oil also caused potassium ion leakage. Differences in the susceptibility of the test organisms to tea tree oil were also observed and these are interpreted in terms of variations in the rate of monoterpene penetration through cell wall and cell membrane structures. The ability of tea tree oil to disrupt the permeability barrier of cell membrane structures and the accompanying loss of chemiosmotic control is the most likely source of its lethal action at minimum inhibitory levels.
J Appl Microbiol 2000 Jan;88(1):170-5. doi: 10.1046/j.1365-2672.2000.00943.x. PMID: 10735256 ncbi.nlm.nih.gov

Mechanism of action of Melaleuca alternifolia (tea tree) oil on Staphylococcus aureus determined by time-kill, lysis, leakage, and salt tolerance assays and electron microscopy
Christine F Carson 1, Brian J Mee, Thomas V Riley
Abstract
The essential oil of Melaleuca alternifolia (tea tree) has broad-spectrum antimicrobial activity. The mechanisms of action of tea tree oil and three of its components, 1,8-cineole, terpinen-4-ol, and alpha-terpineol, against Staphylococcus aureus ATCC 9144 were investigated. Treatment with these agents at their MICs and two times their MICs, particularly treatment with terpinen-4-ol and alpha-terpineol, reduced the viability of S. aureus. None of the agents caused lysis, as determined by measurement of the optical density at 620 nm, although cells became disproportionately sensitive to subsequent autolysis. Loss of 260-nm-absorbing material occurred after treatment with concentrations equivalent to the MIC, particularly after treatment with 1,8-cineole and alpha-terpineol. S. aureus organisms treated with tea tree oil or its components at the MIC or two times the MIC showed a significant loss of tolerance to NaCl. When the agents were tested at one-half the MIC, only 1,8-cineole significantly reduced the tolerance of S. aureus to NaCl. Electron microscopy of terpinen-4-ol-treated cells showed the formation of mesosomes and the loss of cytoplasmic contents. The predisposition to lysis, the loss of 260-nm-absorbing material, the loss of tolerance to NaCl, and the altered morphology seen by electron microscopy all suggest that tea tree oil and its components compromise the cytoplasmic membrane.
Antimicrob Agents Chemother 2002 Jun;46(6):1914-20. doi: 10.1128/AAC.46.6.1914-1920.2002. PMID: 12019108 PMCID: PMC127210 pubmed.ncbi.nlm.nih.gov

High Potency of Melaleuca alternifolia Essential Oil against Multi-Drug Resistant Gram-Negative Bacteria and Methicillin-Resistant Staphylococcus aureus
Alessandra Oliva, Silvia Costantini, Massimiliano De Angelis, Stefania Garzoli, Mijat Božovic, Maria Teresa Mascellino, Vincenzo Vullo, Rino Ragno
Abstract
Purpose: Herein, an extended investigation of Tea tree oil (TTO) against a number of multi-drug resistant (MDR) microorganisms in liquid and vapor phases is reported.
Methods: The activity of TTO was tested against methicillin-sensitive Staphylococcus aureus (MSSA), Escherichia coli, and clinical strains of methicillin-resistant S. aureus (MRSA), extended-spectrum beta lactamases producer carbapenem-sensitive Klebsiella pneumoniae (ESBL-CS-Kp), carbapenem-resistant K. pneumoniae (CR-Kp), Acinetobacter baumannii (CR-Ab), and Pseudomonas aeruginosa (CR-Pa). Minimal inhibitory/bactericidal concentrations (MIC/MBCs) and synergistic activity between TTO and different antimicrobials were determined. In the vapor assay (VP), TTO-impregnated discs were placed on the lid of a petri dish and incubated for 24 h at 37 °C.
Results: TTO showed a potent bactericidal activity against all the tested microorganisms. TTO in combination with each reference antimicrobial showed a high level of synergism at sub-inhibitory concentrations, particularly with oxacillin (OXA) against MRSA. The VP assay showed high activity of TTO against CR-Ab.
Conclusion: Evaluation of in-vitro activity clearly indicated TTO as a potential effective antimicrobial treatment either alone or in association with known drugs against MDR. Therefore, TTO could represent the basis for a possible role in non-conventional regimens against S. aureus and Gram-negative MDR. TTO in VP might represent a promising option for local therapy of pneumonia caused by CR-Ab.
Molecules 2018 Oct 9;23(10):2584. doi: 10.3390/molecules23102584. PMID: 30304862 PMCID: PMC6222846 pubmed.ncbi.nlm.nih.gov