Assholes that haven't been fully wiped. Just dirty, but not scat. Come on, people!
my previous gf frequently had a dirty asshole. she'd come over to my place after school (she was working on her phd) and we'd hook up. i never really saw anything on there but when i would rub her anus it would feel kind of gritty and my fingers smelled like shit. pretty sure she usually took a dump at school and just didn't have time to take a shower before coming over to my place.
I love eating assholes, but not dirty ones (or overly dirty ones). I don't get why pornstars don't wipe/cleanup properly when they know they are going to have closeups of their asshole taken...
When I first started dating my girlfriend I could smell her asshole every time we did doggy. I would try hold my breath or press her ass cheeks together. I think she was still to shy to have shits when I was around so she was holding in a Syrian immigrant until I left.