Smile lines are deep folds that extend from the sides of the nose to the corners of the mouth, forming as skin loses elasticity and volume. Over time, collagen and fat depletion cause these folds to become more pronounced, giving the face a more aged or tired look. While smile lines occur naturally, lifestyle habits, genetics, and environmental factors can make them appear sooner and more severe. Dermal fillers and collagen-stimulating treatments can soften these lines, restoring smooth, youthful contours.