How long does vomiting last after stomach flu for 2 year old only does it at night?

1-2 weeks: With a stomach flu or gastroenteritis, the nervous impulses to the gut can be mixed up. Flow though the tract can be irregular causing cramping and sometimes delayed emptying of the stomach. Night-only vomiting is usually related to poor flow and overfilling of the stomach. This limited vomiting does not usually lead to dehydration. Call dr if the vomiting worsens, is pine green or worsens.