Frown lines often referred to as glabella lines, and are furrows/ wrinkles that appear between the eyebrows. Glabellar lines may appear as a single vertical line or as two or more lines and may also appear angled towards the inner corners of the eyebrows. The muscles of the lower forehead contract in a downward direction causing the skin between the eyebrows to crease.  They are caused by the repeated action of underlying muscles associated with facial expression. Years of squinting and frowning tend to leave deep wrinkles in the skin between the eyebrows and on the bridge of the nose, across the forehead and at the corners of the eyes.