elderly rat growth

Question
Hello,
    Our pet rat Eliot is a male, that is a little over two years old, eating well, a little more energetic than usual, but still not too fond of leaving the cage.  This morning we noticed the right side of his jaw was swollen and it appears his tongue is as well. He appeared to be fine yesterday and we don't know what to do.  Any advice?

                                   -Matt and Meghan

Answer
 It may be a dental abscess or ingrown or broken tooth, or it could be a tumor affecting his mouth.  It's also possible that it is an allergic reaction to something.  I would highly recommend you take him to a vet, who will be able to see inside his mouth with a special instrument and let you know what is going on.  If it is an abscess or infected tooth, it can usually be drained with surgery and treated with antibiotics, but something like a tumor would make the prognosis a little more difficult.  If you do find out exactly what is wrong please let me know!  Good luck with your rat!