The human fat used in dermal filler injections is analogous, meaning it comes from your own body. The surgeon will take fat from an area like your abdomen or thighs, clean it, and then inject it into the trouble spots on your face. This is an excellent option for people with severe allergies because your body won’t react to your own tissue. Some of the injected fat will be reabsorbed, so the surgeon will have to initially overfill the injection site. This will make the area look swollen for a few days, until the body absorbs the excess.