'Forehead wrinkles' is the term usually used for horizontal lines on the forehead. Frown lines, or vertical lines that develop between the eyebrows, may also be referred to as forehead wrinkles (see 'Glabellar lines’). Forehead wrinkles and frown lines are mimic wrinkles, caused by activating the muscles of facial expression. More information on the treatment of wrinkles and lines can be found here: Wrinkle treatment.