A rainbow kiss is a sex act that involves oral sex between a man and a woman who is menstruating simultaneously. The act is performed by a person with a penis going down on a person with a uterus during their period, while they also receive oral sex. Once both partners have ejaculated in each others mouths, the couple kisses, mixing menstrual blood with semen in the process, thus the "rainbow" part of the rainbow kiss. The term "rainbow kiss" is a slang term used in sexology. It is considered a fetish and is not a common sex act. The act is performed by consenting adults who share some sort of bodily fluids fetish. Rainbow kisses are not recommended as they can increase the risk of sexually transmitted infections (STIs) and other infections.