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. 2012 Nov;111(5):1985-92.
doi: 10.1007/s00436-012-3045-0. Epub 2012 Jul 31.

Activity of Tea Tree Oil and Nerolidol Alone or in Combination Against Pediculus Capitis (Head Lice) and Its Eggs

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Free PMC article

Activity of Tea Tree Oil and Nerolidol Alone or in Combination Against Pediculus Capitis (Head Lice) and Its Eggs

Emanuela Di Campli et al. Parasitol Res. .
Free PMC article

Abstract

Head lice infestation is an emerging social problem in undeveloped and developed countries. Because of louse resistance increasing, several long-used insecticidal compounds have lost their efficacy, and alternatives, such as essential oils, have been proposed to treat this parasitic infestation. The present study investigated the efficacy of two natural substances: tea tree (Melaleuca alternifolia) oil and nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) against lice and its eggs. Products were used alone and in combination (ratio 1:1 and 1:2) from 8 % dilution. The in vitro effect of natural substances at different concentrations were evaluated against 69 head lice (adults and nymphs) and 187 louse eggs collected from school children in Chieti-Pescara (Central Italy) over a 6-month period. The lice mortality was evaluated for 24 h by a stereo light microscope. The ovicidal activity was monitored by microscopic inspections for 15 days. Tea tree oil was more effective than nerolidol against head lice with 100 % mortality at 30 min and 1 % concentration. On the contrary, nerolidol expressed a more pronounced ovicidal activity inducing the failure of 50 % of the eggs to hatch at 1 % concentration after 4 days; the same effect was achieved by using a twice concentration of tea tree oil. The association of the two substances both in ratios 1:1 and 1:2 combined efficaciously their insecticidal and ovicidal effect; in particular, the ratio 1:2 (tea tree oil 0.5 % plus nerolidol 1 %) acted producing both the death of all head lice at 30 min and the abortive effect of louse eggs after 5 days. These results offer new potential application of natural compounds and display a promising scenario in the treatment of pediculosis resistant cases. The development of novel pediculicides containing essential oils could be, in fact, an important tool to control the parasitic infestation.

Figures

Fig. 1
Fig. 1
Head lice and louse eggs detection. (a) Collection of lice by combing from infested head. (b) Basket for lice. (c) Viable louse egg attached to the hair. (d) Lice and louse eggs treated for experiments
Fig. 2
Fig. 2
Chemical structure of terpinen-4-ol (a), the main component of tea tree oil, and nerolidol (b)
Fig. 3
Fig. 3
Mortality (%) of head lice (adults and nymphs) treated with tea tree oil (a), nerolidol (b), and their combination in ratio of 1:1 (c) and 1:2 (d) at different concentrations (see “Materials and methods”) and control groups, in time. The total number of lice ranged from 2 to 10, for each product and for each concentration
Fig. 4
Fig. 4
Nymph of louse dead after 20 min of treatment with tea tree oil at 1 % concentration (A4) showing the gut rupture (a), with seepage into the thorax (b) and limbs (c), which appeared after 30 and 60 min, respectively
Fig. 5
Fig. 5
Abortive (%) louse eggs treated with tea tree oil (a), nerolidol (b), and their combination in ratio 1:1 (c) and 1:2 (d) at different concentrations (see “Materials and methods”) and control groups, in time. The total number of louse eggs ranged from 8 to 12, for each product and for each concentration
Fig. 6
Fig. 6
Phases of hatching of louse egg, in time. Eye spot (arrow). Operculum with aeropyles (inset). Original magnification ×100. Scale bar = 500 μm

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