Source? 'access to the blood brain barrier' sounds odd. You make it sound like the BBB magically starts in the nostrils and is somehow weak there. That's not how the BBB works. Sure, your nostrils are closer to your brain than, say, your teeth, but not by much.
I’m fairly sure that different body parts do provide easier access to the blood brain barrier. In this case, I would guess that it’s because of the mucous membranes in the nasal cavity. There must be a reason people snort cocaine rather then just rub it on their hands.
