Vampires are night creatures. They only come out at night, because the sun can hurt them or kill them. They are known as the living dead, because they are corpses that rise again when the sun sets. The vampires rise nightly to seek out and feed on their victims. Vampires thirst for blood, for blood is the key to their immortality. Without blood they will die. Their body dries up because of the lack of blood and they will die in agony. The blood refreshes the body and gives them energy and certain power.
The condition that might be associated with vampire legends is porphyria. Vampire's characteristics are similar to those of porphyrics, this might have led to the misconception in the 14th to 16th hundreds that porphyria sufferers are vampires. For more information of porphyria look in Porphyria.
A condition that might contribute to vampires rising from their grave is calaplepsy. Calaplepsy is a suspension of animation. The person can't move or talk and appeared dead. They are able hear and if their eyes are open can see everything around them. In most cases they are presumed dead. Sometime they would awaken before the burial and are said to be alive, causing confusion and many suspicions.
PORPHYRIA SUFFERERS ARE NOT VAMPIRES!!!
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