Essential oils are also very effective against parasites, such as lice, ticks, scabies, intestines and trichomonads. Although toxic to parasites, the oils do not exhibit any toxicity to the human body. Benzyl benzoate, an aromatic chemical, is one of the few officially recognized flavorings. It is applied externally in the treatment of a scab. Benzyl benzoate is naturally present in ylang-ylang, tuberose, and hyacinth oils, but in very small quantities. The antiparasitic action of essential oils is recognized and has been used over the past 1000 years.