An ex vivo, assessor blind, randomised, parallel group, comparative efficacy trial of the ovicidal activity of three pediculicides after a single application - melaleuca oil and lavender oil, eucalyptus oil and lemon tea tree oil, and a "suffocation" pediculicide

Abstract

BackgroundThere are two components to the clinical efficacy of pediculicides: (i) efficacy against the crawling-stages (lousicidal efficacy); and (ii) efficacy against the eggs (ovicidal efficacy). Lousicidal efficacy and ovicidal efficacy are confounded in clinical trials. Here we report on a trial that was specially designed to rank the clinical ovicidal efficacy of pediculicides. Eggs were collected, pre-treatment and post-treatment, from subjects with different types of hair, different coloured hair and hair of different length.MethodSubjects with at least 20 live eggs of Pediculus capitis (head lice) were randomised to one of three treatment-groups: a melaleuca oil (commonly called tea tree oil) and lavender oil pediculicide (TTO/LO); a eucalyptus oil and lemon tea tree oil pediculicide (EO/LTTO); or a "suffocation" pediculicide. Pre-treatment: 10 to 22 live eggs were taken from the head by cutting the single hair with the live egg attached, before the treatment (total of 1,062 eggs). Treatment: The subjects then received a single treatment of one of the three pediculicides, according to the manufacturers' instructions. Post-treatment: 10 to 41 treated live eggs were taken from the head by cutting the single hair with the egg attached (total of 1,183 eggs). Eggs were incubated for 14 days. The proportion of eggs that had hatched after 14 days in the pre-treatment group was compared with the proportion of eggs that hatched in the post-treatment group. The primary outcome measure was % ovicidal efficacy for each of the three pediculicides.Results722 subjects were examined for the presence of eggs of head lice. 92 of these subjects were recruited and randomly assigned to: the "suffocation" pediculicide (n = 31); the melaleuca oil and lavender oil pediculicide (n = 31); and the eucalyptus oil and lemon tea tree oil pediculicide (n = 30 subjects). The group treated with eucalyptus oil and lemon tea tree oil had an ovicidal efficacy of 3.3% (SD 16%) whereas the group treated with melaleuca oil and lavender oil had an ovicidal efficacy of 44.4% (SD 23%) and the group treated with the "suffocation" pediculicide had an ovicidal efficacy of 68.3% (SD 38%).ConclusionOvicidal efficacy varied substantially among treatments, from 3.3% to 68.3%. The "suffocation" pediculicide and the melaleuca oil and lavender oil pediculicide (TTO/LO) were significantly more ovicidal than eucalyptus oil and lemon tea tree oil pediculicide (EO/LTTO) (P < 0.0001). Ranking: 1. "Suffocation" pediculicide (68.3% efficacy against eggs); 2. Melaleuca oil and lavender oil (44.4%) pediculicide; 3. Eucalyptus oil and lemon tea tree oil (3.3%) pediculicide. The "suffocation" pediculicide and TTO/LO are also highly efficacious against the crawling-stages. Thus, the "suffocation" pediculicide and TTO/LO should be recommended as first line treatments.Trial RegistrationThe study was listed at the Australian/New Zealand Clinical Trial Registry (ANZCTR): reg. no. 12609000884202.

Terpenes: Natural Products for Controlling Insects of Importance to Human Health—A Structure-Activity Relationship Study

“…Consequently, the use of naturally occurring insecticidal compounds could be an attractive alternative to control head lice, including those which are resistant to pesticides [14]. Many scientific studies have proposed the use of various natural compounds, with essential oils having been shown to have different activities such as repellent, ovicidal, and adulticide properties in a variety of insect species, including head lice [3,11,13,[15][16][17][18][19][20][21][22][23][24][25][26][27]. Essential oils and terpenes have also been used in combination with conventional insecticides, and the results of these experiments have demonstrated an increase in the pediculicide properties of synthetic compounds [15,28].…”

Insect bite reactions

“…[86] Treatment Increasing resistance and adverse effects have raised concerns about head lice treatments, [87] encouraging search for new treatments [ Table 4]. [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103] No available pediculicide is 100% ovicidal, and resistance to lindane, pyrethrins, permethrin, and malathion has been reported. [100] Nits persist after the treatment and may be mistaken for active infestation [ Figure 5].…”

“…[99] Hot air Desiccation A non-chemical treatment using a machine producing controlled hot air, [100] 30-minute application of hot air used to desiccate the lice. One study demonstrated nearly 100% mortality of eggs and 80% mortality of hatched lice, [101] another showed overall mortality of lice and eggs as 94.8% and no adverse effects.…”

Assessment of ototoxicity of tea tree oil in a chinchilla animal model

“…Tone burst stimuli (8,16,20,and 25 kHz) with Blackman envelope were presented at 80 dB sound pressure level then decreasing to the threshold. The ABR threshold was determined at the lowest intensity where three reproducible waves were produced.…”

“…Tea tree oil (TTO) is an essential oil derived from the leaves of Melaleuca alternifolia found in Australia. The medicinal properties of TTO were first reported by Penfold in the 1920s and since then have been thoroughly examined by numerous in vitro studies and in vivo [8][9][10][11][12][13][14][15][16][17][18][19][20]. These studies provide conclusive evidence supporting the antibacterial, antifungal, antiviral and anti-inflammatory properties of TTO.…”