Why after an accident should it be nil by mouth if the patient needs to go to hospital?

Eating or drinking after an accident, and prior to being seen by a doctor, carries many risks, which is why patients are told to avoid doing so until they are evaluated. Some injuries, especially to the esophagus, stomach or gut, may not be immediately evident. If a patient eats or drinks, the introduction of a food or liquid bolus into the gastrointestinal tract may worsen symptoms or make a possible rupture worse.

If a patient eats or drinks, and vomits, it can cause dangerous complications to the airway such as aspiration pneumonia and choking.