About an hour ago, I was standing on my deck when I witnessed a car accident - the driver had lost control and drove his minivan headfirst into a tree. I called 911 while running over to see if everyone was OK. Because I live in a busy neighborhood, several other people were able to get there before me (Though I was apparently the first person to think about calling 911!? Bystander effect much?). Several people were trying to attend to the driver who had sustained a head injury and had an open, bleeding scalp wound. Someone had applied a towel/pressure and was keeping the man from moving or trying to get out of the vehicle.
Meanwhile, on the other side of the vehicle, the passenger had already gotten out of the vehicle and was trying to walk. As I ran over, I yelled to the people standing there to get her to sit down and lean back against the vehicle and not move any more than she already had. As I got there, multiple people were asking her questions, despite the fact that she was clearly in shock.
Here's the kicker. At least 3 different people tried to offer her (the passenger) water.
So, for the sake of anyone who may not know, or who may know and be responding to the fact that water treats shock, DO NOT GIVE WATER (or food) TO AN ACCIDENT VICTIM, even if they are in shock. There are several reasons for this.
First, they may choke on it. The choking may be caused by unknown injuries to the neck, or in case the victim is in shock or suffered a head injury, signals from the brain controlling swallowing and gag reflexes may be compromised. While choking is bad enough, it may also exacerbate internal injuries from the physical exertion of trying to cough.
Second, in the event of a head injury that may or may not show visible symptoms, fluid in the body may rush to the head and cause brain swelling... giving a person water gives the body more fluids to send there.
Third, if you happen to give cold water to a shock victim, you can make things significantly worse, even if it is otherwise warm outside. The body has difficulty regulating its temperature during shock due to changes in blood flow and distribution. The sudden introduction of cold water into the core of the body can cause the person to slip deeper into shock.
So, please please please... if you see and respond to an accident or to any situation in which a person may have unseen injuries or be in shock, remember this. No food. No water. Nothing by mouth.
Ninja Edit: Grammar.