"All essential oils have antibacterial properties, but each oil is only effective against certain bacteria.  At the same time as being toxic to bacteria, most of the oils are completely non-toxic to the human organism, the best example of this being tea-tree oil.  It is the single most effective and least harmful anti-microbial essential oil."

Reference:  Robert Tisserand, "To Heal and Tend the Body", Lotus Press, Wilmot, WI, 1988, p. 73.