BOTOX and fillers are both injectable products that reduce the look of wrinkles, so it’s easy to confuse the two. But they work in very different ways. BOTOX relaxes the muscles that cause wrinkles, while fillers use various active ingredients (most commonly hyaluronic acid) to add volume and fill in wrinkles from beneath the skin. Fillers can also be used to add shape to the cheeks and fill in other areas of the face.