Quote:
There are a number of different syncope syndromes which all fall under the umbrella of vasovagal syncope. The common element among these conditions is the central mechanism leading to loss of consciousness. The differences among them are in the factors that trigger this mechanism.
Triggers
Standing up very quickly
Stress
Any painful or unpleasant stimuli, such as:
Venepuncture
Experiencing intense pain
Experiencing medical procedures with local anesthesia
Giving or receiving a needle immunization
Watching someone give blood
Watching someone experience pain
Watching or experiencing medical procedures
Sight of blood