According to Dr. Jordan Rullo, a certified sex therapist at the Mayo Clinic in Rochester, Minnesota, an ass-licking rim job is definitely something people enjoy, but exactly how many people do it is unknown.

“There are no studies on the prevalence that I’m aware of,” Dr. Rullo says. “The prevalence of having ever had anal sex with an opposite-sex partner—according to the Center for Disease Control and Prevention in 2011—is 36% of women and 44% of men. I would guess that these would be the individuals who would be more likely to try oral-anal contact.”

But rimmer beware: It may not be entirely safe.

“Rimming is one way to contract hepatitis and other intestinal parasites, like E. coli,” Dr. Rullo explains. “Partners in long-term monogamous relationships, however, share much of the same anal flora. So if you’ve been in a relationship with someone for more than a couple years, rimming is much safer for you than if you’re with a new partner.

“Sometimes anilingus happens accidentally during cunnilingus, and couples may not address the elephant [or anus] in the room,” Dr. Rullo offers. “If this happens to you, as the giver or receiver, take the time to talk to your partner about rimming as an addition—or if you didn’t enjoy it, an exclusion—to your sexual repertoire.”

Dr. Rullo has more advice for couples engaging in anal sex: Beware of cross-contamination. “Vaginal penetration after anal penetration can lead to infection,” she says. “Never go from the anus to the vagina without a wash break and application of a new condom. If a condom was not used, washing the penis after anal sex isn’t enough, as bacteria can still be inside the urethra. You need to not only wash your penis, but also urinate.”

Likewise, Dr. Rullo explains that, when switching from anal to vaginal penetration with fingers, you should make sure the wash break includes thoroughly cleaning your fingernails.

It’s a lot to worry about, but the payoff might be worth it. “There are a lot of delightfully sensitive nerve endings in and around the anus, and some people really enjoy having that area licked and massaged,” says sex expert Elle Chase. “It’s a pleasure zone for both men and women that can add a great deal of fun excitement to an already enjoyable act.”