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Dr. Kara
Dr. Kara, Veterinarian
Category: Cat
Satisfied Customers: 16705
Experience:  Over 20 years of experience as a veterinarian.
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A couple of days ago, the very tip of my 9-year-old male

Customer Question

A couple of days ago, the very tip of my 9-year-old male cat's lower bot***** *****p became swollen. After some research, I gave him a Zyrtec this morning, but it's still swollen 5 hours later.
JA: I'm sorry to hear that. What is the cat's name?
Customer: Roo
JA: Is there anything else the Veterinarian should be aware of about Roo?
Customer: Indoor cat, no fleas, no unusual scratching, usual peppiness.
Submitted: 3 months ago.
Category: Cat
Expert:  Dr. Kara replied 3 months ago.

Hello, I'm Dr. Kara. I have over 20 years of experience as a veterinarian and I'd like to help. Please give me a moment to review your concerns.

Expert:  Dr. Kara replied 3 months ago.

I am sorry to hear that your kitty Roo has a swollen, bottom lower lip. I believe what he has is a rodent ulcer.

See this link for a picture of a rodent ulcer on the lower lip of a cat:

Rodent ulcers are neither ulcers nor related to rodents. A rodent ulcer is an allergic reaction to something and they can look like a semi-firm swelling of the lip or they may ulcerate and become infected secondarily making them look worse. They are not contagious. They look horrible but many cats don't seem to find them painful and they don't usually interfere with eating or drinking unless they get really big. That means that although this looks terrible to you it is not a true emergency.

The allergic reaction may be to plastic bowls, so I recommend feeding in glass or stainless steel bowls.

These can also be related to a food allergy.

Fish allergies are a common cause. Try to remember if he was given a different flavor of food or treats lately and stay away from that one.

Those things will help stop another from forming and may decrease the size of the one he has now.

Treatment of the current one usually requires oral antibiotics and a steroid injection. So he does need to see a veterinarian. But as long as he is eating well you can have him seen by his veterinarian when convenient this week. Benadryl (diphenhydramine) is great for inhaled allergies, but is not very effective for rodent ulcers.

If it is a continual problem for him then it may be advisable to try feeding a hypoallergenic diet long term to prevent the lesions from coming back.

Rarely, lesions like this can be related to cancer like squamous cell carcinoma or a fibrosarcoma but those are more common in the mouth, either on the hard palate, on the gums themselves or on the tonsils. I have never seen one on the lip, that's how rare they are in that location, so odds are it is more of a benign lesion such as a rodent ulcer.

Let me know if you have any further questions.

Customer: replied 3 months ago.
My research also indicated the possibility of a rodent ulcer. He's been drinking water from a plastic container for over a year, and all was well. I'll give him another Zyrtec tomorrow and if no improvement, will take him to the vet. Thank you for your quick response. Kindest regards, Lynda (and Roo)
Expert:  Dr. Kara replied 3 months ago.

It is possible over time that the plastic surface has been etched with cleaning and there are trace amounts of plastic or chemicals leaching into his water. I recommend stainless steel or glass.

You are very welcome, best of luck with Roo.