Allergies: A misfire between pollen and your immune system

The sneezing, the runny nose, the itchy eyes — it's allergy season.

But what exactly is happening in your body when the pollen starts flying? Dr. Jon Hallberg, medical director of the University of Minnesota Physicians Mill City Clinic, described it as a sort of misguided warfare.

"It's sort of a mismatch or a miscue by the immune system. The immune system helps fight infection; these are not infection, but the body is sort of perceiving it as such," he told MPR News host Tom Crann.

"A kind of white blood cell is breaking open. It's releasing its contents — histamine," Hallberg said. "Histamine goes to blood vessels, causes them to dilate, to ooze a bit, and that's what you've got when you have itchy, watery eyes and sneezing. It's the body's way of trying to expel this invader."

The good news is there's a whole arsenal of medications on the market now. Click play on the audio player above to hear more about when to use an antihistamine, decongestant and steroid nasal spray — and when to see an allergist.