If you have ever enjoyed the scent of a rose, you’ve experienced the aromatic qualities of essential oils. These naturally occurring, volatile aromatic compounds are found in the seeds, bark, stems, roots, flowers, and other parts of plants. Essential oils can also be called as aromatherapy oils.They can be used as single essential oils or in complex essential oil blends depending on user experience and desired benefit. Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of alternative medicine that uses essential oils and other aromatic compounds. Oils are volatilized, diluted in a carrier oil and used in massage, diffused in the air by a nebulizer, heated over a candle flame, or burned as incense. Different essential oils may have drastically different pharmacology. Those that do work well for upper respiratory tract and bronchial problems act variously as mild expectorants and decongestants. Some act as locally anesthetic counterirritants and, thereby, exert an antitussive effect. Essential oils are usually "oil-loving" compounds that usually are not miscible with water. They can be diluted in solvents like pure ethanol and polyethylene glycol. Exposure to essential oils may cause a contact dermatitis. Essential oils can be aggressive toward rubbers and plastics, so care must be taken in choosing the correct handling equipment.