Swollen bottom lip and gums

I just noticed that My kitten Luna (under 1 year old) has an inflamed bottom lip and gums. It's only on one side of her gums, but her bottom lip is worrying me the most. She is an indoor cat and hasn't had any change in her diet. Please help! Very worried kitty mama.

Looks like it could be either cat acne or a rodent ulcer (proper name is eosinophilic granuloma).  If you're not feeding from a stainless steel or ceramic bowl, switch to one and was at least once a day.  However, you need to get her to the vet to have that checked out and get a proper diagnosis.

It looks a bit like an ulcer. Food allergies are most likely to develop if she eats the same thing day-to-day. Chicken, corn, and grains are the most common allergens.

I think it is an ulcer of some sort but please get a veterinary opinion on it.

It probably isn't acne since there is no black flaking. Acne in cats produces black flecks that flake off the skin and is easily mistaken for fleas.

Ulcers can also be an autoimmune issue and triggered by stress. Has your routine changed recently or have you changed food, litter, or have you had new people in/out of your house?