I'm writing about vampires in my story and I'm curious what exactly it is about sunlight that makes them vulnerable to it.

Are there any books or stories that define why the sunlight kills them? Wouldn't the reflection of sunlight off the moon cause a similar problem? I know that the reflection off the moon is only 1/5th (could be wrong, but I know it's a small amount) but wouldn't it still be an issue, or has it been explained that its just not enough sunlight to cause death to them?

I've read a lot of vampire stories but none of them really explain why it kills them that I can think of.

If there are no specific reasons, are there any scientific theories that would be plausible if vampires were real? UV, Radiation ect?


Well for starters there are diseases that get nick named 'Vampire Disease'. Porphyria being the most well known. The actual disease of allergy to Ultraviolet Radiation is called Solar Urticaria, and is pretty rare. I have this disease myself and while it is horrible, it's not life threatening.

Most of the 'historical' reasons for why Vampires burst into flames is mostly Christian/ Hollywood magic. These were vile 'demonic creatures where anything light and holy would destroy them. Crosses, the sun, holy water, etc.

In a more modern setting the moon could definitely effect vampires. You could write something that during the Full Moon your vampires are weakened slightly, but they aren't incapacitated.

All in all I think it really depends on the context of your story. Is this a modern story where science can debunk things? Or is it a fantasy story where any reason could cause it? You could have it where for some reason the UVA/UVB light is damaging on a cellular lever for some obscure scientific reason. Or it could be that the Vampires were children of the moon and humans children of the sun, and the sun is a vampires weakness and the moon is the humans weakness and maybe they avoid going outside in the moon because of it. There are all sorts of possibilities! :D

As far as a scientifically speaking you might want to go the route of a severe allergy, but that the don't exactly burst into flames(maybe the bursting into flames came about as a fishermans tale so to speak, where each time it was retold the story was exaggerated). Maybe their bodies are extremely sensitive because they have a heightened immune system(immortality explanation as well ;) ) when their body absorbs the Ultraviolet radiation it interacts with the mast cells in the skin. The mast cells release histamine and can cause a severe anaphylactic shock!

My best suggestion is to take a look at these already existing diseases: Solar Urticaria, Mastocystosis, Mast-cell activation disorder, Xeroderma Pigmentosum, and of course how or why the body might produce an excessive amount of histamine! :) I hope that helps!!!

Edited to add: Conditions such as Solar Urticaria for example have a wide range of sensitivities. For instance, my sensitivity is on the severe end. I break out in hives from being under light bulbs that emit UVA. All of the bulbs are LED in my house. All of my TV's and computer screens are LED backlit. Lights that emit UV include fluorescent, incandescent, halogen bulbs and more. So depending on the sensitivity your characters may have to wear a special suit. I myself have to wear a special suit to go out in the sun. Even going out at night under a full moon is dangerous for me. I've had reactions under the full moon at night before. But I do always carry my epinephrine with me just in case!

You can also look up the Xeroderma Pigmentosum suits that they have to wear for some inspiration or other ideas. Those are extremely bulky suits but the suit that I wear is composed entirely of a double layer of UPF 50+ rating material(check out the link for what the ratings mean). Although in a fantasy story it would be completely plausible that they have a type of cloth that is such a tight weave it blocks out 100% UV so they don't have to wear a double layer!







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    $\begingroup$ I had a great aunt who had a very bad case of Porphyria. She almost seemed like a witch because she couldn't go outside without completely covering herself head to toe in black garments (gloves included). She had a prescription for extra tinted windows in her car and spent most of her time inside. Apparently even a tiny bit of sunlight would make her skin bubble with 3rd degree burns. $\endgroup$ – Faulkner Jan 7 '17 at 22:03
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    $\begingroup$ Benjamin this idea that you are talking about is actually pretty similar to an interesting theory about myths. Some people believe the Hercules was actually an ordinary man who had a lot of things happen to him. They believe he was a great hero. But each time the story of him was told it became exaggerated to what it is today. It's how the man who was as strong as two men, became the man with the strength of a hundred men! This idea would certainly add a lot of dynamic to your story!! $\endgroup$ – Amerilys Jan 7 '17 at 22:07
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    $\begingroup$ @Benjamin there are definitely some pretty believable ideas behind where the idea of vampires came from. A quick google search of "science behind vampirism" or "how vampires could be real" or "vampire like diseases" will leave you with a plethora of information all of which is right up your ally!! I'm excited for you. :D $\endgroup$ – Amerilys Jan 7 '17 at 23:40
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    $\begingroup$ @DonyorM you would be correct that it's not "biblical", that is my mistake. There were many cultures that believed in Vampires, the Catholic/Christian belief is more prevalent among them. $\endgroup$ – Amerilys Jan 8 '17 at 2:25
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    $\begingroup$ @SandyBeach Benjamin isn't "creating" a new type of vampire. His story based of of the myth of vampires(blood sucking bursting into flames etc) and how they aren't actually like that. That they are more "human" like than the propaganda would have the populace believe. $\endgroup$ – Amerilys Jan 11 '17 at 21:00

Well in the original story of Bram Stokers Dracula the sun did not affect him like we think, it was the first movie adaption that gave us that idea take a look below:


which lists scenes from Bram Stoker's novel where Dracula appeared in sunlight. Apparently he prefers the night but isn't bothered much by daylight.



  • $\begingroup$ Interesting info, I hadn't read that before. Thanks for the links! $\endgroup$ – Benjamin Jan 7 '17 at 23:25
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    $\begingroup$ Please edit this answer to summarize the interesting tidbit from the links. Link-only answers are frowned on. $\endgroup$ – SRM Jan 8 '17 at 2:41

Many stories depict vampires with pale, ghostly skin.

It is often suggested that their lack of pigmentation is due to decreased exposure to sunlight: if you don't go outside as often (because it hurts you) you don't need a reason to develop pigment, so you will end up pale.

This can be reversed. Your vampires will burn because they're pale - they aren't pale because they burn.

Their bodies produce less pigment, so the sun is harsh, and it's easiest to stay active during the night.

  • $\begingroup$ So, you are saying that lack of some pigment can kill you in few seconds of exposure of sunlight? $\endgroup$ – Mukul Kumar Jan 8 '17 at 8:46
  • $\begingroup$ @MukulKumar Short of Amerilys' anaphylactic shock, none of the answers listed here provide a science-based way to kill using sunlight. A severe sunburn seems pesky enough to keep them out of the light, however. $\endgroup$ – Zxyrra Jan 8 '17 at 16:37

The reason vampires are depicted as being threatened by sunlight is more allegorical: Vampires are manifestations of evil or the unbridled human Id (take your pick) which is generally represented by darkness, while good (or the human Superego) is represented by light (a good idea is often depicted as a cartoon lightbulb, for example).

So a lot of this will depend on the nature of your story. Are your vampires real or allegorical manifestations of evil or unbridled emotion? Then light is the opposite and unmasks them/drives them away/destroys them. You could also turn this on its head by postulating a hyper rational vampire (using its cold and calculating nature to carefully study its intended victim and plan the hunt, kill and escape: a perfect crime even a modern criminologist could not solve). These vampire would then be a creature of light (logic) and shun the darkness.....

So long as you are using vampires as mythological or allegorical creatures, there is actually not need to get into "how" sunlight destroys them (much like no one ever gets into how spaceships maintain one gravity fields perpendicular to the floor in SF movies and TV shows, or why the magical sword glows in the presence of evil).

  • $\begingroup$ In my story "vampires" aren't actually real, but the traditional strengths/weaknesses and drinking blood are prevalent in how one society views another (the so called vampires). So I'm looking for ways my misunderstood kingdom of people could debunk the rumors and "truths" about their vampirism. They ARE different and magical in a way sort of similar to a vampire but they actually are something quite different. In my story the word vampire is just a made up word that was blown way out of proportion over several hundred years of history. $\endgroup$ – Benjamin Jan 8 '17 at 3:16
  • $\begingroup$ @Benjamin I guess if "vampire" is an exaggeration, it is easy to explain how drinking blood might get you a disease that would cause photophobia. Easier than explaining how it would cause increased strength anyway. $\endgroup$ – gmatht Jan 8 '17 at 4:40

Well, in reality, all humans have an extremely small amount of phosphorus in the muscle cells for extremely fast movements, but only for an extremely short time. Now assume that vampires are humans that have a mutation that allows them to accumulate much more phosphorus in the cells than normal humans. This can explain two characteristics of vampires:

  1. They can move way faster than any normal human
  2. They will be incinerated by daylight because, as light goes through the skin and reaches the cells, the phosphorus in them will blow up in fire (better by UV light, because it will penetrate deeper into the body)

That is my explanation of Vampires. I hope you can use it.


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