You'd think you know if it were a dream, but I've experienced some rather realistic dreams courtesy of some rather nasty dream crabs.

[ He's just said that with no explanation, just bam, dream crabs are a thing, time to talk about other things. ]

Well obviously the Porter removes the nanites. Some of us, most notably me, can track the nanites. I'd notice back home if my bloodstream was suddenly infested with nanomachines.