I just posted on the Red dyes thread at the top of this section about my dd's annatto intolerance, and her behavior was GREATLY affected by her intolerence. It took a few weeks to get it out of her system, but it is night and day. Almost every member of my extended family (that have seen her at her worst at various times) have commented to me on the change in her. Food hugely impacts our children, and I agree with a pp that if you felt crappy all day, you would be grumpy too! Your description of your lo sounds very much like our DD before we made the changes. She wasn't a biter, but always grumpy, easily angered and usually for no apparent reason, and very slow to calm. (sadly her nickname was "bitter old Eleanor").
I hope you find the culprit. good luck!
