Cosmetic dermal fillers fall into two categories: natural and synthetic. Natural Cosmetic Fillers Fillers derived from natural compounds (the most widely used is Hyaluronic Acid – or HA) have a minimal risk of triggering allergic reactions from their users but extremely rare cases have been known to occur. Characteristics of natural fillers include: • Immediate results • Short life-span (typically from 3 to 18 months) • Most patients need about one ‘follow-up’ dermal injection within the first year • Aside from rare allergic reactions, natural fillers also carry a minimal risk of lumping, although this happens rarely. Synthetic Cosmetic Fillers Synthetic dermal fillers are non-natural man-made compounds that last a lot longer than natural fillers. Some synthetic fillers are considered as ‘semi-permanent’ fillers simply because they really don’t go away. As with any filler, synthetic fillers also have their risks which are the same as natural fillers except that, since synthetic fillers are almost permanent, this means that the potential risks may be longer lasting and harder to resolve with synthetic fillers.