A variation of Body Horror, where a creature is inside someone else, and then leave through an established opening of the body (as in naturally, not a cut or piercing), even if it's not really an opening (like the navel). It could be the mouth, the nostrils, the ear, or through orifices below the belt. Pores could even count. The point is that the orifice is pretty much intact when the creature leaves. Sometimes this can kill the "host", sometimes the host lives, or sometimes the host can already be dead. Contrast Orifice Invasion, Face Full of Alien Wingwong.