I have had a constant runny nose for months now. Why?

I have never had allergies or hay fever my whole life. Since February, my nose has felt like a leaky faucet. And for the past couple of weeks, the back of my throat is burning. My appetite is fine, and I feel fine, other than these symptoms. have never experienced this before. Anyone out here have a hint, clue, or answer? As we grow up, is it possible to start getting allergies, etc., that we had no problem with when we were younger?