Let's talk about mucus. I'm with the Chinese on the subject of nose-blowing. It's disgusting and should never be done in public.
I know someone who's ever so just-so about everything. If the latest fashion is to eat asparagus with a samurai sword that's what we'll find on the table.
And yet, at some point in every meal, he takes out his handkerchief, blows into it mightily, then minutely examines the contents before neatly folding the ghastly package back into his pocket. Once, following such a performance, I couldn't finish my vittles.
Well, now, nasal boffins say blowing your beak makes a cold worse.
It does nothing for a bunged-up hooter and can propel infection-laden gunge into your sinuses.
Mind you, I'm unsure what the alternative is. Decongestant sprays are mentioned, but only in moderation. At other times, if you must blow, then do so in a wild and lonely place.