When a nonsurgical remedy is needed to improve the appearance of an individual, the subject of fillers arises. Fillers are many and varied. One of the first approved fillers on the market was animal collagen. Collagen is complex protein found in all higher animals, and each species has its own specific type of collagen. Popular for many years as the only filler available, it has now been replaced by safer and more effective materials. The problem with collagen is that, because it is a complex protein, it is also "antigenic", meaning that it causes an allergic reaction. This alone can create problems, but it also affects the longevity of the filler effect. In other words, collagen injections do not last very long.