A rainbow kiss is a sexual act that involves the exchange of menstrual blood and semen via lip-to-lip contact. It is performed when a person with a penis goes down on a person with a uterus during their period, while they also receive oral sex. Once both partners have ejaculated in each other’s mouths, the couple kisses, mixing menstrual blood with semen in the process, thus the "rainbow" part of the rainbow kiss. It is usually performed by consenting adults who share some sort of bodily fluids fetish. Some reports suggest that a rainbow kiss is a happy accident that occurs when a person with a uterus coincidentally gets their period while their partner is performing cunnilingus. However, a little planning does go a long way. For instance, it’s crucial that both partners be ready and willing to hold the respective blood and semen in their mouths after performing oral sex, in preparation for that magical kiss. Rainbow kissing is not a new concept, and it is only one of many sex acts people with bodily fluid fetishes perform. It is not a common sex act, and it is not everybody’s cup of tea.