Er, interesting idea. Can we immunize ourselves via the muconasal->oral
route? For one thing, oral innoculation is one classic way to *tolerize*
one's self to an antigen, although this clearly is affected by animal age,
antigen type and concentration. In addition, remember that most things that
go into the nose can be detected in the mouth, as the cavities are connected.
Thus, nosepicking probably doesn't help much. I guess, no, not an important
source of immunization.
