Is Swelling On Lips After Anesthesia For Dental Work Normal?

My 10 year old grandson had some cavities filled tonight. He had local anesthesia and by the time he got home, his bottom lip was swollen several times it's normal size. The fillings he had done were in the top back of his mouth, now where near his lip. This is the second time this has happened to him. Should we be concerned?? My daughter has given him benedryl.