The body is a funny and wonderful thing.

I took pencillin for years as a kid due to throat/ear infections. Then one day boom! Allergic reaction.

You can develop allergies to food or pollen. As a kid I never had an allergy problem. I still live in the same city I was born in but now my allergies kill me.

The only way to find out if this has happened is to take the suspect food out of your diet for a few weeks, then try it again.
If it gives you a headache or other ill feeling you probably are allergic to it.