I Woke Up,with One Eye Nearly Swollen Shut. Not Itching

I woke up,with one eye nearly swollen shut. Not itching or red, nor painful. I don't see or feel any bite or wound, no bruising, I took a benedryl. It's about 12 hours later now and I noticed the swelling in top lid is reduced, still puffy underneath, but my one pupil is very large ! I don't have any pain or fever. No twitching to headache. I am not on any daily meds , but do take an occasional Xanax. I did use eye drops earlier, but once I saw that pupil enlargement, I stopped. Any sugg? Thank u