Most vampire myths come to us from the Dark Ages, when science was in its infancy and people looked to religion or superstition to explain the world around them. While some vampire myths have their basis in Christian Orthodoxy and Victorian romanticizing, others represent imaginative interpretations of actual vampiric characteristics and behavior. Seeing as how they thrive on deception, it's also highly likely that many of these myths were perpetuated by vampires themselves in order to gain an edge over their ill-prepared victims, to instill more fear in the populace, or to gain more followers.
Presented in no particular order:
Kurt Barlow from Salem's Lot
Vampires sleep in coffins
Source: This myth likely arose from gravediggers and passersby who observed vampires emerging from coffins and crypts.
Fact: If a vampire did spend the night in a coffin, it probably had nothing to do with sleeping preference. In the old days, many bite victims were interred while still in a vampiric coma—which in-turn gave birth to the myth that vampires must sleep within the soil of their homeland. The truth is, they will sleep wherever they feel safe. That's not to say some don't choose to sleep in coffins, although it's more out of a sense of ritual or tradition than an actual need (besides the perk of keeping out light and sound).
Garlic repels vampires
Source: Most likely based on observation. To ward off vampires, garlic would be worn, hung in windows, or rubbed on chimneys and keyholes.
Fact: Vampires have sensitive noses and can be momentarily driven off by pungent odors. However, this method of deterrence is unreliable and certainly won't work on an experienced vampire. Basically, you'd be better off using pepper spray.
Horror of Dracula
Crosses repel vampires and burn their flesh
Source: Christian beliefs that vampires are demons and therefore enemies of God. During the Dark Ages, vampires were known to have been tortured by the church using superheated iron crosses to "burn the Holy Spirit into them" before execution.
Fact: Unless heated by fire or used as a bashing or throwing weapon, crosses have absolutely no effect on vampires. They have no trouble entering churches, either.
Vampires can be killed by driving a stake through their heart
Source: This myth actually started out as a misguided method of keeping suspected vampires in their coffins by driving a long iron stake through the torso and into the coffin floor, effectively pinning it in place. Eventually this evolved into simply stabbing the heart using special kinds of wood—such as oak, ash and hawthorn—which were thought poisonous to vampires because of the "purity" associated with trees and nature.
Fact: Because their blood clots quickly and is circulated by skeletal muscles, vampires can easily survive injuries to the heart and torso; and they have little trouble freeing themselves from impalement. They also have no apparent allergy to wood (or silver, for that matter). When fighting vampires, your best bet is to aim for the head or spine.
Vampires burst into flames upon exposure to sunlight
Source: Most likely based on observation of a vampire's extreme reaction to sunlight, and possibly mixed up with their vulnerability to fire.
A vampiric patient is set ablaze in Let the Right One In.
Fact: Sunlight renders vampires, with their hyperdilated irises and reflective retinas, blind. It also causes neural pathways to fire randomly in the brain, creating an extreme epileptic reaction. On top of that, vampiric skin is highly sensitive to UV rays, becoming badly burned and blistered within minutes. However, as dramatic as these reactions may appear, not even a hint of smoke will occur.
Holy water burns vampiric flesh
Fact: Holy water, or any water for that matter, has little effect on vampires. They can, however, still be drowned; and they generally hate getting wet as it can lower their body temperature, making them less energetic and able to hunt.
Vampires prey on virginal women
Dracula whispers sweet nothings to his next victim.
Source: A reflection of 19th-century fears over the sexual awakening of young women. In Balkan and Bulgarian folklore, male vampires were believed to deflower virgins and even impregnate them with half-human hybrids known as dhampir.
Fact: While vampires have a stated preference for the taste of young blood, they are not particular as to which gender provides it. Being asexual, sterile and impotent, they also cannot have intercourse, let alone produce any kind of offspring; and biting a pregnant woman will only result in miscarriage or stillbirth.
Vampires can fly & move at the speed of sound
Source: Embellished accounts of vampires running, leaping and using their cat-like reflexes.
The Strain featuring its bloodthirsty main antagonist, who can move like the wind despite having once-crippling gigantism
Fact: While they can sprint faster than most humans (25 to 30 miles per hour) and jump higher than any (at least ten feet), vampires cannot fly, levitate, teleport, or move any faster than a top-tier athlete.
Vampires can turn into bats
Source: Association of vampires with vampire bats, since they're both nocturnal and utilize pointed fangs to feed on blood. More importantly, both species are the main vectors for the human vampirism virus. As a result, they were typically believed to be different forms of the same creature.
Fact: Vampires cannot turn into bats, or anything else for that matter. Although vampires can't shapeshift (or retract their fangs), their appearance does change over time, and they can be quite adept at disguising themselves using makeup and other appliances.
Vampires do not cast shadows & are not visible in mirrors
Source: Christianity. It was thought that a vampire, or any creature lacking a soul, would not cast a shadow or produce a reflection.
Fact: Like any typical disease, vampirism has no effect on the body's ability to block or reflect light. However, considering the fact that vampires tend to avoid light altogether and are often quite uncomfortable with their own reflections, this myth has a slight grain of truth to it.
Vampires shed bloody tears
Source: Vampires typically have red, bloodshot scleras—the so-called "whites of their eyes." Because of this, people throughout history have come to believe that vampires have bleeding eyes.
Fact: Because their blood is confined to the eyeball, vampiric tears are just as clear as ours (unless they wear mascara).
American Horror Story: Hotel
Humans become vampires by drinking infected blood
Source: 19th-century sexualization of vampires and their victims "exchanging" bodily fluids.
Fact: While it's true that the vampirism virus is also carried in the bloodstream, transmission almost always occurs through biting. Contrary-wise, human ingestion of vampiric blood tends to induce vomiting, while injection can be outright lethal.
Vlad III, aka Prince Dracula
Elizabeth Báthory & Vlad the Impaler were vampires
Source: Their alleged penchant for drinking the blood of the people they killed. This eventually inspired Victorian author Bram Stoker's famous vampire character Count Dracula.
Fact: There exists no verifiable evidence that Countess Báthory and Prince Dracula were biological vampires. Even the notion that they drank blood is dubious at best, being a likely fabrication to further demonize them. Still, "behavioral vampirism" was not uncommon throughout history, as hematophagia was suspected to be the sole reason behind vampiric longevity before modern science disproved that claim.
Vampires have psychic, hypnotic & telekinetic powers
Dracula's brainwashed thrall, Renfield
Source: The common vampiric ability to read subtle emotions, and their reputation for using their "silver tongue" to get what they want. Telekinesis was simply thrown in later as a baseless supplement, likely due to the superstitious association of vampirism with witchcraft and the occult.
Fact: While vampires do have heightened senses thanks to their enlarged amygdalae, they cannot read minds or see the future—only physical expressions and mannerisms. This in-turn benefits their powers of persuasion, as they can more easily subvert their victims on an emotional level. Logically, such abilities depend greatly on individual skill and experience. Their enhanced hearing also allows them to talk discreetly amongst each other—an act easily mistaken as telepathy.
Interview's Louis lamenting his eternal sideburns
Vampires retain the same appearance as the day they were turned
Source: 19th-century romanticizing of vampiric longevity, in addition to their common use of makeup; and possibly the fact that child vampires remain permanently stunted after transformation (although such individuals were quite rare, given the high death toll of young coma victims).
Fact: Older vampires actually look more like Nosferatu's Count Orlok—or, more accurately, anorexic drowning victims with alopecia and pinkeye. On a related note, the myth that a vampire's hair never changes most likely came about from its slowed growth rate, as well as their tendency to wear wigs after it falls out.
Vampires can choose to live on only animals and blood bags
Source: Hollywood idealization of vampirism as something that can be rehabilitated and reintegrated into human society.
Fact: Although animals and blood bags can get them by for a while, vampires ultimately have to feed on live humans to get all the nutrients they require.
A vampire's wounds can heal within seconds
Source: Likely an exaggeration of vampiric dexterity.
Fact: While it's true that even major injuries can clot within a few minutes, vampiric healing rate is only double that of a human, and they can still suffer prominent scarring. As for regeneration of lost body parts, they can regrow their upper and lower fangs, but nothing else.
Slain vampires become ash
Source: Most likely the practice of cremating slain vampires to prevent the possibility of infection, as well as the selling of their ashes in some parts of the world.
Fact: Dead vampires actually decompose at a slower rate than human corpses, thanks to natural antibiotics in their bodily fluids.
Count von Count
Vampires can be distracted by leaving seeds for them to count
Source: Due to changes in the part of the brain that regulates habitual activity, vampires are more susceptible to mental disorders such as arithmomania, or the obsessive counting of objects. Some forms of porphyria—often mistaken for vampirism—have also been linked with such conditions.
Fact: Regardless of how severe a vampire's OCD might be, counting objects is a low priority when faced with a potential meal or threat.
Vampires absorb ingested blood directly into their veins
Source: Association of hematophagia with blood transfusions.
A female mosquito digesting blood while excreting excess fluid to make room for the more solid nutrients
Fact: While many fictional vampires are depicted as being able to fully absorb undigested blood through a variety of methods—hypodermic fangs, larger pores in the GI tract, fusion of the stomach and vascular system, reconnection of the esophagus into the heart—the truth is that vampires digest blood no differently than hematophages such as vampires bats, leeches and ticks (or even how we digest our own food).
Vampires have the strength of 20 bodybuilders
Source: Exaggeration of vampiric strength; further embellished in Bram Stoker's Dracula.
Fact: Drop the zero and you have a more accurate number. A vampire is usually quite a bit stronger than the average bodybuilder, but not so much as those on the upper end of the scale—the ones squatting 1,000 pounds and bench pressing 600. Details aside, the leaner-bodied vampires still have speed and agility on their side when faced with heavier-muscled humans.
The vampire race can be traced back to a single progenitor
Source: Association of vampires with demons, fallen angels, half-angels, and biblical creation myths—such as the legend of Lilith, who was said to be Adam's first wife before leaving him to spend the rest of her existence feeding on the blood of men.
Fact: While it's true that many organisms can be traced back to a most recent common ancestor (such as Mitochondrial Eve), and infectious diseases to an index case or "patient zero," there is no all-powerful mother or father of all vampires—not one that's still living, at least. One grain of truth to the Lilith legend, however, is that vampires have very likely been around for as long as humans have (if not longer), since Adam and Lilith were said to be created at the same time and from the same source.
Vampires have a prominent widow's peak
Source: Observation of early-stage hair loss. This eventually inspired numerous Hollywood villains such as Bela Lugosi's portrayal of Count Dracula, along with typical depictions of Lucifer or Satan.
Fact: Like typical male-pattern baldness, early vampiric alopecia creates a receding hairline where hair is lost from above the temples but not the front and center of the scalp. This resulting widow's peak is most apparent after about a year of vampirism. Within a couple more years, the remaining upper hair is eventually lost as well, before additional baldness spreads further down the rest of the scalp over the next few years until there's nothing left but bare, blue skin.
Human ear pointing isn't too different from the tissue loss experienced by older vampires.
Vampires have pointed ears
Source: An actual characteristic of older vampires, which may be a possible reason why mythical immortal beings like elves and fairies usually sport pointed ears themselves.
Fact: While not the elongated bat ears of some depictions, vampiric ears do experience a degree of shrinkage over the years—almost like shriveling leaves—causing the ear helix to fold or crumple into a subtle point.
Vampirism can cure any human ailment
Source: The vampiric ability to ward off a multitude of diseases including cancer.
Fact: Although vampirism can effectively cure a diseased human, such individuals have a much harder time surviving the transformation process—especially with advanced age and most definitely with organ transplants. On top of that, debilitating injuries remain largely unaffected—although it can prevent degenerative conditions (like Alzheimer's) from progressing further. In addition, vampires with cerebral palsy and ALS can potentially recover a limited degree of fast-twitch motor function, while the blind and deaf may regain some hearing and night vision. This, of course, depends on the severity of such disabilities prior to infection.