My allergies have always caused post-nasal drip, and the cruddy drips would soon cause sore throat. I used to have congestion with it too, and if I took pseudoephedrine (alone, not mixed in any combination pill), it would dry it up & squelch the congestion
AND the post-nasal drip. Now it's controlled to a degree, because of the meth culture, so you either need a prescription for it, or you at least have to sign for it at the pharmacy.
I can't speak to the sneezing, because I've been a sneezer all my life. Friends made fun of it when I was a teenager; even tonight in the restaurant where we celebrated better half's birthday, I sneezed three times after I'd finished the meal. Once in a San Francisco airport restaurant, I sneezed and the waiter said 'gesundheit', so my
ORNERY better half grabbed the opportunity to tell him six more sneezes would follow, and they had a rousing good time counting them as they did indeed follow - six more exactly. If they were delicate ladylike sneezes, I wouldn't even mind, but they're elephant sneezes!

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(click all the little sneezies)