Collagen is the main structural protein found in our bodies, and can be derived from a human or animal source (typically pig or bovine) for cosmetic use. Collagen fillers are largely a thing of the past, due to the higher probability of allergic reactions, and unpredictable longevity. Having an allergic reaction to collagen fillers should not rule out treatment with Juvederm. Juvederm, as well as the majority of fillers currently on the market, are made of a synthetic version of hyaluronic acid, a naturally occurring molecule found in the human body. Unlike collagen fillers, allergy tests prior to treatment are unnecessary, due to the very, very low probability of an allergic reaction. If you would like to be extra cautious, you may first have a “test spot” injected in an inconspicuous area, and monitor the area for any reactions in the following days. You will likely find no change, and may move forward with treatment shortly thereafter. Be sure to first consult with a board certified Dermatologist. Best of luck.