If I know that I'm about to blow a load (ie I'm sick or my allergies are kicking ass), I excuse myself and go to the bathroom.
If it's just one sneeze and the nose is runny, I'll still excuse myself, go off somewhere and blow my nose. I'll make sure that my back is facing them so they don't see me actually blowing it.
In my opinion, someone who's nose is super runny and keeps on inhaling just to keep the load in is more annoying than someone who chooses to blow their nose in public, especially when you start seeing the post nasal drip.