Lemon balm (Melissa officinalis) is a herb in the mint family. Often said to help ease stress and anxiety, lemon balm contains rosmarinic acid (a chemical compound with antioxidant properties). The herb is also used for insomnia, cold sores, high cholesterol, genital herpes, indigestion, and heartburn. In essential oil form, the scent of lemon balm is used to reduce stress.