YoungDonk, why do you mock his question then proceed to give good advice? Strange.
From what I know, women's ass is very different from men's ass. It's a rare woman who want you to just jump right in there. Generally when I'm going down on a girl, and she comes, that's a good intermission to start licking her asshole before getting back to her pussy. So long as everything's clean first that's pretty safe (and always way, way safer than fucking after brushing her ass.)