Hard to say hat things babies can be allergic to other than the usual suspects, ie peanutbutter, etc. How about just stopping for a few days and see if he will improve. If it does improve then wait a few weeks before introducing again. In the meantime you can try other foods. Remember that it isn't necessary for him to eat everything that is suggested. FWIW, both of mine did not like sweet potatoes when they were younger. DD still don't like them and ds just recently likes them. They will eat everything else but not that.
Hope he gets better!
BTW I wanted Xavier to be ds' middle name but dh veto me.
