My cat has a bite on his left side of his face and is swollen. What can I do for it before taking him to the vet. He goes in the closet and I can't get to him until comes out.

I guess wait until he comes out and bring him to the vet. This forum will not be helpful for treatment questions...I've been bringing my dog to these folks for the last five years and I have only good things to say about Beltsville veterinary hospital!

If he were a human I would give him some Benadryl. I don't know how much is safe for a cat.

It would be best to get him to a vet to get him examined. If the bite has abscessed he will need antibiotics and treatment. Try blocking the closet off so he can't access it a day before his appointment so the day of the appointment you are able to catch him and get him seen. If blocking or closing the closet is not an option, try to make your appointment in the morning and you could keep him in a room or bathroom overnight , with a litter box and water. That way you will be able to catch him in the morning for his appointment but he won't need to be confined all day. Best of luck. Kitties can be tricky.