Complications are rare, but can occur. Most commonly, they involve temporary redness, swelling, and bruising that lasts for a few days. Less frequently, there may be persistent swelling, indicating a need for the dissolution of the injected hyaluronic acid. The most severe complication is the accidental puncturing and occlusion of a blood vessel. The blockage of blood supply can lead to severe tissue damage (necrosis) and, in extreme cases, blindness. Such blockages must be considered absolute emergencies and should be immediately resolved with Hylase by trained physicians.