Advice for my sister's cat.

[mayanorange]

I agree with Bicyclista on this one. If the cat is in that bad of shape, there's a problem.

But as far as diagnosis without really seeing the cat, it sounds like it's most likely dermatitis, given the raw lips and chewing. Which could be caused or just aggravated by stress. I'd suggest fish oil supplements if possible. The other thing that can cause raw lips is reactions to bowls- especially plastic ones. Make sure they have a glass, ceramic, or metal bowl and that it is washed frequently. If you're over there, brush the cat and give it some attention- at least it'll get something that way.

PS- sounds like the state I got Sadie in- ignored for 6 mos before her rehome because of a sick child, plus fed crap food, so she had dermatitis and an elbow so raw from scratching and gnawing it reeked. We've gotten her skin and most of her coat back to normal with some good food, fish oil and vitamin e everyday, proper grooming and exercise.