Expression lines occur due to the repetitive and sometimes excessive use of facial expression muscles. Over time, repetitive use of the muscles of facial expressions such as brow-raising, frowning, blinking, smiling and even smirking can result in permanent expressive lines (frown lines, forehead wrinkles, crow’s feet, bunny lines, gummy smiles and lines around the mouth).
After years of repeated muscle contraction compounded by sun damage and aging, these lines can become permanently etched into the skin.