The Snowballing (sexual practice) reference article from the English Wikipedia on 24-Jul-2004
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Snowballing (sexual practice)

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Snowballing is a rare human sexual practice in which one person takes into his or her mouth the semen of another person (either from ejaculation or from where the semen was ejaculated to), at which point the semen is then swapped back and forth between one or more people through kissing or spitting.

Because it involves exchange of bodily fluids without any barrier, it is not a form of safer sex. Risks are presumably similar to those of unprotected fellatio.

While most people do not find snowballing particularly appealing or are even disgusted by it, the practice is sometimes shown in pornography.