[jyl]

My daughter fell off some playground equipment, got knocked out, then threw up, a friend went to the school to get her, she threw up a couple more times in the friend's car and house (a very good friend). She was 5 or 6, no lasting ill effects. So I'd not hesitate to take him back to the doctor - please err on the side of caution, may do it even if he doesn't omit again but is simply feeling like vomiting - but I would try to be calm, it does happen to lots of kids.

(How come we never see professional boxers vomiting after a knockout?)