Can allergies (runny nose, sneezing & watery eyes) turn into a sinus infection?

Yes, it happens to me a lot. Drinking a lot of water and taking anti-histamines and decongestants help quite a bit.

Yes, if you get bacteria up into your already irritated sinuses. Sure.

If you are blowing out yellow/green mucus, it's infected. See your doctor for an antibiotic. You don't want to mess with infections in your head. Dangerous to not get them treated correctly.
yes any matter that is left in the sinuses can become infected
nurse
Yes! I finally had to have a sinus surgery to correct the issue.
Yes, I know they can. Bacteria which enjoy the micro-environment of the sinus and nasal passages can thrive there.

Another reason not to pick your nose.
Yes you can, I had a sinus infection due to my allergies (don't they suck). You can become so congested that it builds up and builds up and doesn't have a way to escape your body. Check out the following web site and you can put your symptoms in and see whats up. Hope you get better!!!