We don't scan the body with this device. However, if you're making contact with, let's say, cocaine or whoever packed your baggage might have some cocaine on them, that trace residue is usually transferred into that area, or your toiletry kit, or whatever else.
The scan from the ion scan will help the officer identify whether you might be carrying something, whether it be body packed or around your person, in your shoes, in your pockets, in your jacket, or quite often, within a false-sided suitcase or whatever it might be.