Hi Jade,
My dd may have an allergy/intolerance to banana - we're not sure yet - it corresponded w/a cold (her symptoms are GI related, vomitting, etc). But a LO can have an allergy to any food - no rhyme or reason. Most food allergies are outgrown, but some aren't (clear as mud huh?). You could try again in a couple of months and see how she does. Since she had a reaction though be careful introducing other foods - do them one at a time and for at least 4 days.
Good luck!!