Swollen lower lip

Any ideas what could cause this? Simon is indoors-only and while all the cats tussle, they don't do any serious fighting. He is eating (canned food diet) and drinking normally and does not seem to be in pain. Should we go to the vet next week?

I am a human doctor, not a cat doctor, and it is always difficult to diagnose from a photograph.  However it could be a number of things, such as a reaction to a bite, an insect sting, an allergic reaction or an infected tooth.  Today is Saturday and, if it has not improved by Monday, then I would certainly take him to the vet.

With all best wishes,

Geoffrey

Hi @parsleysage...I agree with @Geoffrey, that it could be a number of the things that he mentioned.

I would definitely take him to the Vet.

It also reminds me of a recent thread I was on, in which 'LavishSqualor' mentioned "feline eosinophilic granuloma" which are commonly called "rodent ulcers".

This other thread mentions it a bit more:

http://www.thecatsite.com/t/264792/cat-has-swollen-lower-lip-pictures-included

It may not be that, though, but I think your Vet would know.

Also, if you are feeding Simon from plastic dishes, it's a good idea to switch to stainless steel, in case he has an allergy to plastic, or some bacteria which can get into the scratches in plastic.

Update us next week, when you can, since it would be helpful knowing what your Vet says.

Thank you all so much, I am glad to know it is not super urgent (my vet does have Saturday hours) but still a cause for concern, that gives me a sense of what to look out for. We are in the process of getting rid of fleas so it's a possibility it's an allergic reaction to a bite... however, we have had fleas for awhile (been fighting them "naturally" to no avail, so got the house professionally treated 2 weeks ago, the cats of course get monthly treatments) and nothing like this has ever happened for him in the year or so we have had fleas. Maybe it just built up over time? I know that happens in human sometimes where they suddenly develop an allergy. Thank you for the link on "rodent ulcers"! I will look into that. They eat from ceramic/glass dishes and ceramic water fountain, no plastic, but thank you very much for the responses and feedback! 

One of my kitties had this for a a week or so. Colloidal silver cleared it right up!