The maximum-strength ointment kills fungus once it is applied. It contains terpinen-4ol (a substance that kills bacteria and yeast). Fungalspores can enter skin through a receptive surface like your nail. Undecylenic acid can be used to treat toenail-fungus. Kerassentials oil is a natural oil made of high-quality ingredients such as tea tree oil and lemongrass oil, flaxseed oils, flaxseed oil and vitamin E. Make sure to use a salon which uses pipeless footbaths. However, a thickened nail can be a point of entry for bacteria that could lead to limb-threatening infection.