Why cant boogers be smelt?

Answer 1

Actually, they can. However, the body produces the sticky form of mucous that turns into boogers in order to trap harmful particles in the air that you breathe in order to keep them from reaching the vastly more important lungs, where they can do some serious damage. As things dry out, including mucous, they become less smelly, as smell is a function of tiny particles of the substance in question flying off in the air and being detected by our nostrils. So, boogers have very little water left in them, are sticky in the first place, (so as to TRAP particles, not release or emit them), and are thus hard to detect any smell of. They DO smell, though, primarily of the particles that they trapped (house dust, smoke etc), and less so of the original goop that they were made of. Since smell is supposed to clue you in as to what is helpful and what is harmful to ingest (see my answer to "what tastes better..."), and since mucous isn't particularly harmful OR helpful to eat, it has a neutral smell to begin with.