New research has been released investigating the effectiveness of two natural substances, tea tree oil and nerolidol, against head lice and eggs, suggesting high levels of pediculicidal and ovicidal activity.
The paper by Di Campli et al., published in the July 2012 edition of Parasitology Research, conducted in vitro trials of pediculicidal and ovicidal activity using solutions of tea tree oil and nerolidol, two naturally-occuring active compounds.
The assays were conducted on a sample comprising 69 lice and 187 eggs collected from schoolchildren.
Each oil was applied to lice and eggs in up to an 8% solution and mortality was measured over a 24 h period. Combinations of the two oils in a 1:1 and 1:2 tea tree:nerolidol ratio were also tested in up to 8% total active concentration.
Strict criteria were used to determine lice and egg mortality, requiring the absence of either internal or external vital signs.
Tea tree oil was found to induce lice mortality in 100% of samples when applied in a 1% concentration. By contrast, nerolidol only produced 33% mortality in a 2% concentration.
When the two compounds were combined, complete mortality was observed using sub-2% concentrations (ingredients in both a 1:1 and a 1:2 ratio).
The cause of death in most cases was due to gut rupture. The authors speculate that the pediculicidal effect of the oil comes about via blockage of the respiratory system.
The best results for ovicidal activity were given by the 1:2 mixture of tea tree:nerolitol (total concentration 1.5%), which induced complete ovidical effect after 5 days post-treatment.