Oregano oil is one of the strongest antibacterial oils there is, and it smells like it. Up to four fifths of it is carvacrol, a phenol that punches holes in bacterial membranes until the cell leaks. Reviews of carvacrol credit it with killing bacteria and fungi, calming inflammation and protecting cells.^[1] In lab tests the whole oil stopped bacteria forming the slimy films that shield them, at doses too low to kill them outright.^[2] It is a strong skin irritant and needs heavy dilution.^[3]