Many classic horror icons and other disturbing creatures share common characteristics. Pale skin, dark, sunken eyes, elongated faces, sharp teeth, and the like. These images inspire horror and revulsion in many, and with good reason. The characteristics shared by these faces are imprinted in the human mind.

Many things frighten humans instinctively. The fear is natural, and does not need to be reinforced in order to terrify. The fears are species-wide, stemming from dark times in the past when lightning could mean the burning of your tree home, predators could be hiding in the dark, heights could make poor footing lethal, and a spider or snake bite could mean certain death.

The question you have to ask yourself is this:

What happened, deep in the hidden eras before history began, that could effect the entire human race so evenly as to give the entire species a deep, instinctual, and lasting fear of pale beings with dark, sunken eyes, razor sharp teeth, and elongated faces?

I think lots of dangerous predators have sharp teeth and dark eyes; humans are quite special in that we have noticeable eye whites, and that we can use our eyes to communicate certain things.  If you cover your eyes when you meet someone, by wearing sunglasses for example, then people are a little less likely to trust you.  And sunken faces and pale skin would naturally be associated with sickness and death.