Cat's lower lip is red and swollen

[Maggiez]

For the past 2 days ago my boy Loki's lower lip has been red and today it's a bit swollen. Other than that, he's completely healthy, eating and playing as usual.
We can pet him just fine, even rubbing his face and side lips, so I don't think he's in pain.
I've read a few threads from this forum and it seems like it's a common issue with various causes.
I did not change his food or any other routines.
He's an indoor-only cat and haven't seen any indication of fleas.
I only feed him from stainless steel and ceramic bowls. His favorite toy is a plastic spring, but he has been playing it for months without any issues.
The only thing I can think of is a piece of plastic packaging he was chewing on, on the first evening that he showed the redness. The next day I spotted the plastic and threw it away immediately. But today it seems like it's getting worse.
Is there anything I can do to help pinpoint the cause and help him recover?

 

[di and bob]

It looks like it is either an insect bite or from the plastic toy/ packaging. It looks like an allergic reaction anyway. Take away anything plastic, and see how that goes. This will take at least a few days to resolve and it takes a long time for the hair to grow back. As long as he is not hiding, eating, drinking, and using the litter box, everything should be OK.

 

[Maggiez]

Thank you! I'm not sure it's an insect bite because it's winter here and we usually leave the windows closed. I'll try my best to removed the plastic items (didn't realized how many things are made in plastic until now!) and wait a few days. Hopefully it's not a big issues and he will recover soon.

 

[di and bob]

Oh, he should. Just watch for pawing at his mouth, or hiding , a sign of pain. I'll bet he is fine in a week or so.

 

[verna davies]

It could be a rodent ulcer, easily treated with meds from your vet. Are you able to post the photo to your vet.

 

[Maggiez]

I actually never thought about remote diagnose. During covid regulation, I took Loki to the vet once and he saw him at the clinic without letting me going inside. I didn't like the practice because it made him miserable. I'll wait a few days and see if he's getting better. And I'll ask the vet if it's possible to do a remote diagnose. Thanks for the advice!

 

[Maggiez]

It looks like it is either an insect bite or from the plastic toy/ packaging. It looks like an allergic reaction anyway. Take away anything plastic, and see how that goes. This will take at least a few days to resolve and it takes a long time for the hair to grow back. As long as he is not hiding, eating, drinking, and using the litter box, everything should be OK.

Reporting back:
You're totally right!
It took about 1 week for the swollen to go away. And now his hair is slowly growing back.
On top of removing potential hazard, I also wash their bowls and food mat more frequently. In the past I might leave the bowls out f there's food in it, but now I wash them more promptly because I gave them raw food.
I also got an immune booster from my local holistic pet store and I add a few drops to his food every day. Hopefully it helps preventing future infection.
He was playing a lot and eating as usual during the time. But looking back, I did notice that he spent more alone time on the top of the cat tree and rarely asked me to pet him (he is shy and vocal, so I can only pet him when he asks me to). These days he's more cuddly and requests more petting and has been spending more time with me. Now I know that cats are really good at hiding their pain.