Tea tree oil: an insight on the Aboriginal bush medicine

The Tea tree plant Melaleuca Alternifolia, the source of tea tree oil, has been in use for centuries by the traditional people of Australia.
Often prepared by soaking in water overnight or applying the crushed leaves directly, it was used as an antiseptic for skin wounds and as a treatment for sore throats, coughs, cold and fever. It was even used by white settlers, until the popularity of modern antiseptics and antibiotics took over in the middle of the 20th century.

But is there any merit in this old bush remedy?

As it turns out, this simple plant has shown its ability to assist in the recovery from many ailments, from acne to more complex afflictions such as MRSA (Methicillin Resistant Staphylococcus Aureus).
MRSA has become a huge problem in recent decades, known for infecting hospitalised patients particularly with topical wounds. This bacterial infection is extremely difficult and expensive to treat as it has become resistant to hardy antibiotics (13).

Tea tree profile

Melaleuca Alternifolia is native to north-eastern New South Wales and south-eastern Queensland. It grows into a small tree with thin, linear green leaves, pale papery bark and fluffy white flowers. Melaleuca alternifolia produces an oil which ranges in colour from pale yellow to clear with a strong and distinctive odour, and is extracted from the leaves by steam distillation (1).

Properties

As well as being an effective antiseptic, it is also an anti-fungal, antimicrobial and anti-inflammatory agent.

• It has been demonstrated in the laboratory to kill salmonella and E. Coli bacteria (responsible for food poisoning, diarrhoea, urinary tract infections), streptococcal species (which causes sore throat and fever), candida albicans, enterococcus species (responsible for urinary tract infections) and staphylococcus aureus, among others (15).
• It has even been shown to kill certain types of cancer cells (in tests done on the isolated cells) (12).
• Tea tree oil is toxic in large amounts if ingested; a 25 mL bottle is enough to severely affect a small child, and thus should only be applied topically unless advised by a medical professional (1).

The Research

Sadly, the majority of publications on tea tree oil and its uses are either anecdotal (the experiences and/or stories of individuals) or very small-scale studies, and often tea tree oil is tested on isolated bacteria rather than infected patients.

Those that do report testing on infected patients are very small scale, uncontrolled and often use combined treatments. These results unfortunately do not allow for reforms on how bacterial infections are treated in hospitals, but it does highlight the need for large-scale clinical research, as tea tree oil exhibits potential to augment treatment in so many areas.

• Tea tree oil was first distilled in 1925, and its antiseptic, antibacterial and antifungal effects were described in a dental magazine. It was used extensively by non-native Australians during the 20th century and by Australian soldiers in the Second World War as an antiseptic. It was thought to be so vital to the soldiers, that those involved in its production were exempted from military service (15, 17).
  Tea tree oil fell out of favour after the Second World War due to the rising popularity of penicillin.

During the latter part of the 20th and early part of the 21st century, several studies were performed to determine its efficacy in treating a range of ailments.

• In 1990 it was determined to be just as effective at treating acne as benzoyl peroxide, and had less chance of severe negative side effects, though it was slower acting than the peroxide (6).
  In fact, the most common severe side effect of tea tree oil treatment is contact dermatitis.

• In 2001 it was shown in a small scale study of 10 patients to be beneficial at treating cold sores (14).
  Another study found that a 5% solution of tea tree oil was more effective than a placebo at treating dandruff, resulting in a 41% improvement in symptoms (11).
• In 2003, it was shown to be effective, both in the lab and when tested on rats, at treating antibiotic resistant and sensitive strains of candida albicans (which is the cause of oral and vaginal thrush infections) (4).
• In 2004, one of the main and best understood components (terpinene-4-ol) was shown to be effective against the scabies mites.

How tea tree oil works

It is thought that tea tree oil’s effectiveness comes from two main components terpinene-4-ol and linalool. These compounds are called terpenes and have a variety of therapeutic effect, you can read more on linalool here.

These constituents have been shown to affect the structure of the bacterial cell wall, compromise the cytoplasmic membrane and interrupt transcription of proteins, which stops the bacteria from growing and reproducing, and induces their death (1, 16).

43.8% of the essential oil of Melaleuca contains caryophyllene oxide, a terpene commonly found in lemon balm and Cannabis. (19) In the plant, it serves as an insecticidal/anti-feedant, shielding from herbivores and insects, as well as a broad-spectrum
antifungal to further defend the plant. (20,21) Analogously, caryophyllene oxide demonstrated antifungal efficacy in a model
of clinical onychomycosis (tinea) comparable to ciclopiroxalamine and sulconazole, with an 8% concentration affecting eradication in only 15 days. (22)

The effects of tea tree oil on skin issues are very consistent. It has also been shown in human and mouse studies to be an effective anti-inflammatory to treat histamine induced skin inflammation (1).

Possibly one of the most interesting pieces of information to have been discovered about tea tree oil is its ability to kill strains of the staphylococcus aureus bacteria that are either sensitive or resistant to the antibiotic methicillin. Infections of this type can be extremely difficult to treat, as methicillin is a particularly strong antibiotic.

Two separate studies found that, in the lab, the minimum concentrations of tea tree oil needed to inhibit 90% of s. aureus growth are 0.32% and 0.5% respectively. At these concentrations the tea tree oil solutions were not strong enough to kill the beneficial bacteria that already inhabits our skin, which may help to maintain normal skin flora during treatment (1).
It has been reiterated in several studies from varying disciplines that tea tree oil could be a useful addition to bacterial infection treatment regimens. There are documented accounts of addition of tea tree oil assisting in clearing up chronic infections in human patients effectively, with and without antibiotics, and in less time than anticipated. Much more research is needed, though, before tea tree oil can be used to its full potential (1).

 There are difficulties in performing more clinical research on tea tree oil, as the concentrations of compounds within the natural products can vary greatly, the individual ingredients are often complicated and difficult to isolate in a lab setting, and determining any synergistic behaviour can be a mammoth task depending on the number of compounds within the plant. Another big hindrance is the lack of patent control over natural products, which may be a research deterrent to big pharmaceutical companies. However, it can clearly be seen that this wonderful plant could be the hero of the antibiotic resistance crisis that we’ve been looking for, and deserves our attention.

Tea tree oil in everyday life

Tea tree oil comes in many preparations, from the neat essential oil to a component in a cream or gel. Companies now manufacture products including deodorant, essential oils and a skincare range for acne treatment.

Tea tree is also available in water soluble solutions which can be applied directly to treat ringworm, tinea, acne, insect bites, disinfect small cuts and abrasions, or diluted to add to a vaporiser for chest complaints or to disinfect the home. Different additives in preparations containing tea tree oil may affect its efficacy, but none have been found to diminish the antimicrobial effects (17).

Patch testing on the wrist or forearm is recommended to determine if an individual’s skin may be sensitive to tea tree oil before using to treat for any of the above. Tea tree oil has been shown to aid so many different ailments with so few side effects that its addition to any home first aid kit or skincare routine would not go amiss.

References

1. Halcón, L; Milkus, K. Staphylococcus aureus and wounds: A review of tea tree oil as a promising antimicrobial. Am J Infect Control. 2004 Nov;32 (7): 402-408
2. Mantil, E; Daly, G; Avis, T. Effect of tea tree (Melaleuca alternifolia) oil as a natural antimicrobial agent in lipophilic formulations. Can J Microbiol. 2015 Jan; 61(1): 82-88.
3.   Packer, J; Brouwer, N; Harrington, D, et al. An ethnobotanical study of medicinal plants used by the Yaegl Aboriginal community in northern New South Wales, Australia. J Ethnopharmacol, 2012 Jan;139(1):244-255.
4. Mondello, F; De Bernardis, F; Girolamo, A; et al. In vitro and in vivo activity of tea tree oil against azole-susceptible and -resistant human pathogenic yeasts.
5. J Antimicrob Chemother. 2003; 51(3):1223–1229
6. Walton, S; McKinnon, M; Pizzutto, S; et al. Acaricidal Activity of Melaleuca alternifolia (Tea Tree) Oil – In Vitro Sensitivity of Sarcoptes scabiei varhominis to Terpinen-4-ol . Arch Dermatol. 2004 May;140(5):563-566.
7. Bassett, IB; Pannowitz, DL; Barnetson, RS. A comparative study of Tea tree oil versus benzoylperoxide in the treatment of acne. Med J Aust. 1990 Oct;153(8):45-&
8. Hammer, KA. Review Treatment of acne with tea tree oil (melaleuca) products: A review of efficacy, tolerability and potential modes of action. J Antimicrob Agents. 2015 Feb; 45(2):106-110.
9. Budhiraja, SS; Cullum, ME; Sioutis, SS; et al.Biological activity of Melaleuca alternifolia (tea tree) oil component, terpinen-4-ol, in human myelocytic cell line HL-60. J Manipulative Physiol Ther. 1999 Sep:22(7):447-453
10. Umbidong, E. Bush Medicine at Uluru (Olden Times and Today) [online]. Aborig Isl Health Work J. 1983 Sep;7(3):27-28
11. Nabarula, A; Nabarnardi, C; Nambijimba, E, Peterson, S. Bush Medicines Used at Warrabri [online]. Aborig Isl Health Work J1978 Dec;2(4)12-14.
12. Satchell, A; Saurajen, A; Bell, C; Barnetson, R. Treatment of dandruff with 5% tea tree oil shampoo. J Am Acad Dermatol. 2002;47(6):852-855.
13. Liu, X; Zu, Y; Fu, Y; Yao, L; Gu, C; Wang, W; Efferth, T. Antimicrobial axtivity and cytotoxicity towards cancer cells of Melaleuca alternifolia (tea tree) oil. Eur Food Res Technol 2009 Mar; 229:247-253.
14. Healthy WA – Health information for Western Australians. MRSA [Internet]. Australia. Government of Western Australia Department of Health. Available from: http://healthywa.wa.gov.au/Articles/J_M/MRSA (Accessed 6/8/17)
15. Carson, C; Ashton, L; Dry, L et al. Melaleuca alternifolia (tea tree) oil gel (6%) for the treatment of recurrent herpes labialis. J Antimicrob Chemother, 2001; 48:450-451
16. Saller, R; Berger, T;  Reichling, T et al. Pharmaceutical and medicinal aspects of Australian tea tree oil. Phytomedicine 1998;5(6):489-495
17. Cuaron, J; Santosh, D; et al. Tea Tree oil-induced transcriptions alterations in Staphylococcus aureus. Phytother Res. 2012; 27(3):390-396
18. Thomsen, PS; Jensen, TM; Hammer, KA et al. Survey of the Antimicrobial activity of commercially available Australian tea tree (Melaleuca alternifolia) Essential Oil Products In Vitro. J Atl Comp med, 2011; 17(9):835-841
19. Farag RS, Shalaby AS, El-Baroty GA, Ibrahim NA, Ali MA, Hassan EM (2004). Chemical and biological evaluation of the
    essential oils of different Melaleuca species. Phytother Res 18:30–35.
20. Bettarini F, Borgonovi GE, Fiorani T, Gagliardi I, Caprioli V, Massardo P et al. (1993). Antiparasitic compounds from East African plants: isolation and biological activtiry of anonaine, matricarianol,canthin-6-one, and caryophyllene oxide. Insect Sci Appl 14: 93–99.
21. Langenheim JH (1994). Higher plant terpenoids: a phytocentric overview of their ecological roles. J Chem Ecol 20: 1223–1279.
22. Yang D, Michel L, Chaumont JP, Millet-Clerc J (1999). Use of caryophyllene oxide as an antifungal agent in an in vitro
    experimental model of onychomycosis. Mycopathologia 148: 79–82.