Essential oils. Close-up of bottles of myrrh, tea tree and thyme essential oils. Essential oils are the chemicals that form the odoriferous essences of plants. They are extracted from the flowers, fruits, leaves, roots, seeds and bark of many plants. Essential oils impart flavour and delicate aroma to coffee, teas, wines and liquors and are used in the manufacture of perfumes, soaps and disinfectants. Many also have important medicinal uses. Myrrh can be used as a stimulant tonic and an antiseptic in mouthwashes and toothpastes. Tea tree oil has antiseptic properties. Thyme makes an antiseptic gargle or expectorant for coughs and catarrh.