This is an excellent question that seems very simple but has a lot of subtleties surrounding it. This horizontal wrinkle or fold often occurs after people get Botox around their mouth for vertical lip lines. Immobilizing the circular muscle around the mouth to eliminate those vertical lines can make their horizontal neighbors worse. This horizontal line can be made better with Botox, but this is NOT just treating the area around the mouth as most people normally do. You want to be very careful who you visit about this because you can lose function around your mouth if it is overdone or improperly done. Everybody likes to smile, talk and eat normally, so beware. To ensure you are receiving the highest level of care, seek out a modernly trained, new-school dermatologic surgeon, oculoplastic surgeon, facial plastic surgeon or plastic surgeon who is board certified and fellowship trained in one of these "core four" cosmetic specialties. Cameron Chesnut#realself500 Physician