perhaps it is something being caused by an allergen that you are breathing in and it could make nauseated.. but you're sneezing and getting it back out of your system
Believe it or not it can be a reflex symptom of gastritis. It can stimulate the Vagus nerve, which carries all abdominal organs sensation, as well as the ones from the throat and respiratory tract.
This can be a sign of a sinus infection or respiratory infection. The act of sneezing stirs up mucus that then either puts pressure on the inner ear, affecting balance, or is swallowed, causing an upset stomach.
It's possible that your inner ear is very sensitive to fluctuations with in the membranes of your sinus and ears. When you sneeze a lot of tissues get compressed and shuffled around.
