About 25 years ago I figured out I was allergic to corn -- was reading Dr Doris Rapp's book on allergies and some of the symptoms she listed and non-standard matched how I felt after eating pop-corn --
when I removed it from my diet (99% corn free) -- my daily migraine headaches went away, along with a host of other symptoms that a doctor would have loved to put me on forever meds for. All symptoms cleared up within 1 month of excluding corn from my diet.

In retrospect, my symptoms had increased for a number of years - as food manufacturers began the switch from cane sugar to corn syrup. I now, as a mater of course read every label in the store - even if the item was safe before..