PARIS: Dairy’s bad too because of the mucous. You haven’t had any dairy in the last forty-eight hours, have you?
RORY: In my cereal this morning.
PARIS: Geez! Okay, well there’s a solution of salt water and vinegar that can help cut that.
Paris (who is allergic to dairy herself) tells Rory that she isn’t allowed to have any dairy foods before the debate, because it stimulates the production of mucous. It’s commonly believed, but in fact this is a complete myth. There is simply no link between drinking milk and producing more phlegm. It’s thought that because milk and saliva form a moderately thick liquid that briefly coats the throat and tongue, it gives the illusion of having increased phlegm, hence the reason for the mistaken belief.
However, she is correct that vinegar is a natural decongestant – the usual home remedy is apple cider vinegar with honey in it. Salt water is also an excellent gargle to clear the throat, so it seems as if Paris has put the two things together to create what she must think is a doubly-powerful remedy. I’m hoping she only intends it as a gargle – drinking salt water is obviously bad for you, and might make Rory sick.