The Food Lion milk had a product date from January 11 to January 20. The serial number is the UPC code which is the same on all the milk they sell even today. I hope you did not have milk that when out of date Jan 20th, I doubt it. If you thought it was the milk you should have taken the milk with you to the ER and had them test it. I had this happen to my son when he was 10 and i took what i thought was the offending food with me and it was not that food. Unless your daughter only drinks milk then you can not tell what it was. It could have been from dirty hands as well.