The only consistent sign of loss of consciousness is that the person is no longer aware of, or responsive to, his or her surroundings. A person who is unconscious does not appear to respond to sound or touch. Many times, the person quickly regains awareness, similar to "waking up" after fainting. In more serious situations such as a severe head injury, a person may remain unconscious for a long period of time. A coma, which is a state of unconsciousness from which a person cannot be aroused, may last for hours, days, or even years.
Other signs and symptoms are related to the specific cause of the condition. For example, an individual who loses consciousness as a result of a head injury may have a bump on the head or a bleeding wound.