The U.S. Food and Drug Administration qualifies collagen as and injectable dermal filler and lists multiple side effects of its use. Collagen can cause common and rare side effects, which can be temporary or permanent.
Common side effects of collagen include bruising, redness, swelling, pain, tenderness, and rash. Other effects include granulomas, infection, allergic reaction, and necrosis. Several rare side effects were reported to the FDA and shared on their website. Those rare side effects included movement of collagen from injection site to other areas of the body, leakage of material at injection site, and vision abnormalities. These side effects can occur if the collagen is used in approved or unapproved instances as stated by the FDA.