Fillers

Fillers are gel-like substances that are injected beneath the skin to restore lost volume, smooth out lines around nose and mouth (a.k.a. marionette lines, smile lines, and parentheses), enhance & restore volume to sunken cheeks or temples, diminish vertical lip lines, plump & enhance the lips, smooth out a chin crease, and improve symmetry among facial features.
Potential Side effects
After the injection, some common injection-related reactions might occur. These reactions include: erythema, swelling, bruising, pain, itching, infection, post inflammatory nodule, sequelae thereof, or tenderness at the implant site. Typically, resolution is spontaneous 24-48 hours after injection in the skin, and two to seven days after injection in the lips.
Additionally, palpable lumpiness and a light blue/gray color within the skin have been noted after use in some patients. There is a potential risk with any injectable that the material could be inadvertently injected into the dermal blood vessels, which could lead to vascular occlusion in the end-artery with corresponding consequences (necrosis, blindness, stroke).
Lastly, there is a remote risk of allergic reactions causing prolonged raised lumpiness, itching, and possible abscess and anaphylaxis to local anesthetic.