Fig. 1 Macrophages were incubated with tea tree oil or terpinen-4-ol or alpha-terpineol for 24 h. Bars indicate the mean percentage + SEM of viable cells in the cultures relative to the control (set at 100 %). Different letters indicate significant differences between groups in terms of macrophage viability (ANOVA and Tukey post-test, p\0.05)negative