I do not know what I am allergic to. About once or twice a year, I start getting sniffies and watery in one eye so I am allergic to something.

About 4 days ago, my throat starts to hurt when I swallow. In the beginning of this, my one eye was watery so I started taking Sudafed then switched to Mucinex. It still hurts. I am not coughing out anything and I seldom get the sniffles now.

Should I be really concerned or will it just go away in time?

I don't know if allergies cause sore throat, but they do cause Post Nasal Drip which causes sore throat.

I get a runny nose after I eat certain foods. My throat hurts right now too and it's frustrating trying to figure out what I'm allergic to.

Try to determine where you were when it happened or what you were eating. Some allergic reactions happen right after you come in contact with the allergic food/chemical/pollen/etc... which gives you a decent chance of figuring it out.

Try gargle (or gurgle ) salt water. It helps for me. Make
the salt water touch the part in the throat the sore ( I know
it's deep ).