an arginine bath is soaking someone in cum, preferably in the facial region. (Semen) All semen and the seeds of some trees (cum trees) contain a primary amino acid called L-Arginine. The unique smell of jizz and these particular trees come from this amino acid. If you'd like to verify this, go to GNC or any vitamin store and ask to smell some arginine you and hopefully your girl, will recognize this right away.
My girl is so dope because she lets me give her the arginine bath right on her face, like a porn star!