Immediately following a Kybella treatment, there will be some swelling, bruising, and numbness under your chin. It's also normal for the area to puff up and lose any definition for the short term as the injectable fat-fighting abilities go to work. The swelling, which is an indication that Kybella is working, is often the worst at the 24-hour mark and can last anywhere from a few days to a few weeks. However, with each following treatment, the swelling, numbness, and bruising will become less and less since there is subsequently less fat to treat.