Why does my daughter throw up when she gets really excited she'll laugh then get hiccups then vomits i have no idea why?

VOMITING: When she gets excited and hiccups sets in, the vagus nerve is stimulated then vomiting occurs.

Involve same muscles: Coughing, laughing and vomiting involve the diaphragm in all of us and a kid often does not have the nervous system control to keep one activity from bridging to another.As a kid ages, the nerves & control improves & it will be less an issue.