Anything that prevents contact with mucus on your skin would be considered to be helpful in preventing the spread of it, so if your nasal sprays are working for you to keep you from being congested and runny, I would say continue them as long as you are not having any side effects such as nose bleeds, chest congestion and the like.
Do limit your use of them to the time stated on the packaging. Using them for longer can have a rebound effect in that your symptoms may go away and then come back as bad or stronger.
Yes, any irritation whether allergies or infection, can cause your nasal mucus to increase because that is how your nose tries to rid itself of foreign invaders. (I like to think of the game "Space Invaders" when I say that -

.)
Best of luck and let us know if we can help any further!
Lindaru