What Causes Stomachache Followed By Vomiting In A Child?

Hi, my five year old daughter was complaining about stomach pains today and then she said she felt sick. She started to look weak to me, so I had her lay down. This went on for hours. It was lunch time and she wouldn t eat anything except a yogurt which she said made her over full. A short time after she started throwing up all over the floor. And it seems it made her tired because she just sat down and fell asleep in seconds. My sister suggested that she might have billias, but I don t know what it is exactly. What do you think could be the matter please?