Frown lines are the vertical lines between the eyebrows, sometimes referred to as the “elevens.” This is the most popular area injected since these lines cause an unwanted angry appearance. Many people inadvertently contract this group of muscles called "glabella" subconsciously, which results in the formation of these lines between the eyebrows. This occurs with activities such as reading, concentrating, and even thinking. With repetitive muscle use over the years, the moving lines become deeply etched and become present even when not frowning, giving the impression of a permanent scowl. At that stage, neuromodulators are insufficient, and dermal filler must also be injected.