Restylane is a smooth hyaluronic acid filler appropriate for most areas of the face. It is a naturally occurring substance in the body and can be used to soften folds around the mouth, enhance the lips, lift the corners of the mouth, volumize the under-eye area, and reduce lines and wrinkles on the face. The results of Restylane can last between 6-9 months or even up to 1 year, depending on individual factors.