Fillers are injections that are often used to correct small indentations in the skin and fine wrinkle lines, as well as to augment or enlarge the lips. The most common fillers are Collagen and Hyaluronic Acid (e.g. Restylane). Neither is perfect and each has advantages and disadvantages.
Collagen is a natural product developed in the late 1970s but it was not until the early 1980s that it became widely used. The injections are made from cattle by the Collagen Corporation. Collagen is a protein that could potentially cause allergies in humans. Although this can occur it is made less likely by removing the amino acids at the end of the protein (telopeptides). With the exception of the ends of the molecule most of the remainder of the bovine collagen is very similar to human collagen. A test for sensitivity reactions to collagen is usually given about a month before treatment begins.
Hyaluronic acid is a man-made chemical that is less likely to cause allergic reactions but it is more painful to use and more likely to leave a reddish lump for a week or two after injection.
They both last around six months, with a range from a few weeks to almost a year. They are most effective when injected into the dermis, just below the surface of the skin. Most plastic surgeons overcorrect at the time of the treatment because some of the material is absorbed.
Rapid resorption may occur in about one in ten patients. Several treatments are usually needed. It is not a permanent solution to fine lines.