The EXACT thing has happened to me!  EXACTLY!  We DO NOT use amoxicillan now
because the last time we did, my son's face and lips/throat blew up like a
balloon.  And I had told the doctor it would happen, but he literally REFUSED
to give me something else.  I called my pharmacist as well, who could not find
anything in it specifically.  We are sure that the red dye was a MAJOR factor
- we are no longer using things with red dyes because my son gets these
symptoms with red dye.  You may consider that if it was the pink mixture.
Either way, yes, we have had the SAME problem, and like you, never found the
answer.  We even tried the white formula with no luck.

Katherine