Nursing. That's exactly what the ER will tell you. Been there twice. And my DS#2 was throwing up for 10 days, lost three pounds and we were in the ER twice. It was just a bug. He was not listless or anything. Had he been they would have been admitted. But he gladly ate at the breast and puked most of it up, but clearly kept some to keep him hydrated.
BFing, CDing, all natural mama to three boys! Certified lactation Counselor