Percentages of unhatched human head louse eggs after treatments with ddH2O, Nix, NYDA, or NYDA without fragrances over time. An asterisk (*) indicates that the percentages of unhatched eggs were significantly increased compared with the 10 min exposures within a treatment group (ANOVA, P < 0.05). A triangle (Δ) indicates that the percentages of unhatched eggs were significantly increased compared with the 30 min exposures within a treatment group (ANOVA, P < 0.05).