Relatively speaking bbbjcimsw is risky but less of a risk than licking someone's balloon knot.
Rimming risks transmission of Hepatitis A, genital warts, parasites like shigella and giardia, and herpes and syphilis if an open area or sore is present. Any behaviour that potentially introduces someone else’s fecal matter from their GI tract to your mouth—rimming, fingering, or even just sharing sex toys—can do it. You can even get infected from licking or sucking your lover’s balls or butt cheeks after anal sex.
Medical studies regarding the effectiveness of mouthwash to eliminate those STDs, bacteria, etc are inconclusive.
Rimming is risky however even medical professionals take those risks from time to time ..