A Study on the Effectiveness of Tea Tree Oil on Head Lice

I was looking through some of my old files and there are many items I've found and 'saved' for my own information or because I've found them interesting; even though it doesn't mean I'm using them in any way at the time. 
This is one of those.  Apparently, a couple years ago I put this into my document file because I was collecting information on tea tree oil.  This is an oil we use in our home regularly, although I've never used it for lice. I found this article interesting and saved it; I decided I better start posting some of my information files or I, myself, will forget I have them!

A report on these issues was published in Acta Derm Vernereol 1999; 79: 1-2.  Scandanavian University Press.

The increasing resistance of head lice to established insecticides means that patients and parents are seeking alternative effective treatments (1). Essential oils, including tea tree oil and Biz Niz, are promoted as treatments for head lice by alternative medicine therapists. 

Tea tree oil is the essential oil steam distilled from the leaves and terminal branches of tea trees, in particular the Myrtle tree (Melalenca alternifolia) (2). It is a complex mixture of over 100 hydrocarbons and terpenes. Of the 15 compounds found in highest concentration, 12 are monoterpenoids. These include terpinen-4-ol (30%), 1,8 cineole (15%), p Cymene, pinene, terpineol and terpinene (3). terpineol is also an insipient ingredient in some standard insecticide containing louse treatment lotions which are felt to be more effective (4). A 1% copper oleate shampoo (which also contains tetralin) has been shown to be an effective treatment in 1 clinical trial (5).  We examined the potential loucicidal activity of tea tree oil, copper oleate, tetralin, terpinen-4-ol; terpinene, using in vitro exposure tests with freshly collected live adult head lice.

Neat tea tree oil, tetralin, terpinene, terpineol and terpinen-4-ol were diluted to 1% and 10% solutions in isopropanol. Copper oleate crystals were created by combining copper sulphate and potassium oleate according to Nelson & Pink (6) and, from this, 1% and 10% aqueous solutions were made. All products were obtained from Sigma-Aldrich Co., Ltd (Poole, Dorset, UK). Chemical-impregnated filter papers were made by dipping Whatman no. 1 cellulose filter papers, 5 cm in diameter, into the various solutions. The filter papers were dried an stored at 4 degrees C in the dark in air-tight containers and used within 24 h. Live adult head lice were collected off school children (aged 4-11 years) from 3 primary schools using a fine-toothed louse detector comb. Consent for collecting lice was obtained from the South & West research ethics committee, school head teachers and pupil's parents. Lice were pooled together to provide sufficient test numbers. The lice were stored in a portable incubator set at 30 degrees C and 70%; relative humidity (the optimum lice survival conditions) (7) and used in the in vitro test within 2 h of collection. The lice were exposed (10 per filter paper) to the various impregnated filter papers as well as unimpregnated filter papers and assessed after 2 h. Mortality was judged as the absence of all internal and external movement on tactile stimulation.

The results are shown in Table 1. Compared with controls, there was a significant mortality for all chemicals tested, except copper oleate (p Lice were either dead or seemingly unaffected, except for gamma terpinene exposed head lice, which showed hyperexitability, increased abdominal contractions and uncoordinated movements at 1% exposure.

Table I. Mortality of head lice on exposure to potential insecticides

Insecticide Dead Alive
Tea Tree Oil

10% 70 11
1% 0 50


10% 35 26
1% 0 81


10% 50 0
1% 26 75

Copper oleate

10% 0 40
1% 0 43


10% 80 0
1% 23 65

The mechanism of action of these compounds is not known; however, some monoterpenoids and tetralin derivates do have neurotoxic effects (8, 9). Increasing the concentration of monoterpenoids or tetralin in existing pediculocides might improve insecticidal activity, but may also increase the number of reported cases of contact dermatitis or symptoms of overdose. Further laboratory work is needed in order to
establish dose mortality curves and long-term safety data before these chemicals can be assessed using clinical trials. The promotion of commercially available essential oils as treatments for head lice should be discouraged until more data is available.

  1. Downs AMR, Stafford KA, Coles GC. Head lice: prevalence in school children and insecticide resistance. Parasitol Today 1999;15:1-4.
  2. Nenoff P, Haustein UF, Brandt W. Antifungal activity of the essential oil of Malaleuca alternifolia (tea tree oil) against pathogenic fungi in vitro. Skin Pharmacol 1996;9:388-394.
  3. Knight TE, Hausen BM. Malaleuca oil (tea tree oil) dermatitis. J Am Acad Dermatol 1994; 30:423-427.
  4. Burgess I. Carbaryl lotions for head lice – new laboratory tsts show variations in efficacy. Pharma J 1990; 12:159-161.
  5. Iannantuono Rf, Devoto F, Saitta MF, Valicenti MR, Gomez F, Gonzalez C, et al. Pediculicidal activity of antidandruff shampoo in a 1% copper oleate formulation. Adv Ther 1997; 14:134-139.
  6. Nelson SM, Pink RC. Solutions of metal soaps in organic solvents. Part IV. Direct-curent conductivity in solutions of some metal oleates in toluene. J Chem Soc 1954: 4412-4417.
  7. Busvine JR. Evidence from double infestations for the specific status of human head lice and body lice (Anoplura). Systematic Entomol 1978;3:1-8.
  8. Lee S, Tsao R, Peterson C, Coats JR. Insecticidal activity of monoterpenoids to western corn rootworm (Coleoptera: Chrysomelidae), two-spotted spider mite (Acari:Tetranychidae), and house fly (Diptera:Muscidae). J Econom Entomol 1997;90:883-892.
  9. Wyrick DW, Booth RG, Myers, AM, Owens CE, Kula NS, Baldessarini RJ, et al. Synthesis of 1-phenyl-3-1,2,3,4-tetrahydronathphalenes as ligands for a novel receptor with -like neuromodulatory activity. J Med Chem 1993; 35:2542-2551.

You might also be interested in these items available through Amazon;

Melaleuca Tea Tree Oil (1 oz)
Tea Tree Oil (Melaleuca)100% Pure Essential Oil Therapeutic Grade-australian 10 Ml (Tea Tree, 10ml)
Majestic Pure Tea Tree Oil, Triple Extra, 100% Pure and Authentic, 45% terpinen-4-ol, 1 fl. Oz
Schooltime Lice & Nit Comb-- Metal Comb with Ergonomic Handle


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