Botulinum toxin has been used in medical treatments for over 4 decades and was first approved by the Food and Drug Administration (FDA) for the treatment of wrinkles in 1989. It is now one of the most popular cosmetic treatments in the world. It works by temporarily blocking the connection between nerves and muscles, enabling muscles to relax. The injection of botulinum toxin into the masseters, relaxes these muscles and reduces their activity. This makes them shrink in size, giving the jawline a slimmer appearance, without affecting your ability to smile, speak or chew.