We are just going to put it out there: When it comes to anal sex, people worry about getting feces on them. Stubbs says that, so long as the receptive partner has had regular bowel movements, this shouldn't really be an issue. For those who are still unsure, water enemas are an option (avoid castor oil because it can make a mess). Uses of dental dams, gloves, and condoms are also common. The bigger concern (for women) should be the potential transfer of bacteria from the anus to the vagina. If you are switching in that order, change condoms.