Dermal fillers are injectable substances that are used to add volume to the skin and smooth out wrinkles and fine lines. They work by filling in the areas that have lost volume due to aging, sun exposure, or other factors. The most commonly used fillers are made of hyaluronic acid, which is a natural substance found in the body that helps to hydrate and plump the skin. The results of dermal fillers are immediate and can last from six months to two years, depending on the type of filler used and the area treated.