Anal sex is a sexual practice that consists of introducing the penis or a sex toy in case of anal masturbation into the anus or rectum of the partner.
Besides humans, this practice is known to exist among primates and other mammals. Since the Middle Ages, anal sex has been considered a taboo. Over the centuries almost all religions have condemned it.
The reasons for this rejection are varied. On the one hand, anal sex was one of the most used natural measures of birth control; on the other hand, the practice of this sex had high hygienic risks. This disapproval has continued until today. In the United States, for example, in , anal sex was a crime in some states, even if it was practiced in legal marriages. Today, anal sex is one of the most widespread sexual practices among homosexual couples. Through anal sex, infections can be contracted if a condom is not used, since the walls of the anus and rectum break easily, causing small wounds through which bacteria and viruses can reach the bloodstream.
These walls are absorbent, so the blood or semen of the sexual partner can enter the body through the anal mucosa even if there is no wound.
Since the sphincter is normally closed, anal sex may be painful if this muscle has not been previously stretched. To make the practice pleasant for the couple, penetration can be accompanied by masturbation, which helps anal muscles to relax and improves anal penetration.
