Red Bumps on Cat's Lower Lip

[snarkytea]

Hi everyone! My nearly 4-year old cat has some sores that just showed up on her UPPER lip (sorry, couldn't edit the title). They sort of resemble human cold sores - they are in the corner of her mouth only on one side. A few months ago, she had a recurring case of what the vet thought was a corn allergy (we have weaned her off all dry food with corn or wheat in it and switched to the Breeze Litter system since we were using a corn-based litter too), which showed up in a sore on the inside of her upper lip on that same side. Since getting rid of the corn products, the original sore has virtually disappeared but now these little bumps are popping up.

Could it be another allergy? She is fine otherwise - happy, running around, drinking plenty, going to the bathroom, eating (a lot as usual), etc.

I tried to take a photo, but up close, it's hard to tell unless you're in person. And of course, she didn't like sitting still for the photo.