It is performed under local anesthesia. A mild sedative may be given prior to the procedure if the patient does not drive after discharge for at least 8 hours. No surgery is risk free. Fat injection is very safe. You can not be allergic to your own cells.
Infection is possible but antibiotics are taken pre and post-op.
Bruising and swelling are normal. The biggest problem is obtaining symmetry or evenness, but careful molding at the end of surgery and the possibility of future touch-ups make this less of a concern. Risks are outlined in detail in the Special Consent to Fat Injection Surgery . One day is usually sufficient. Strenuous work should be avoided for a 7-10 days.