tl;dr: some psych. did research on creepiness, and it turns out that we may have a creepiness detector built [to alert of us potential threats], but it's pretty shit at its job, and only goes off when the persons seems like they could be scary, but can't tell for sure. And what alerts it tends to be benign, fairly insignificant things such as having pale skin, bags under your eye, or certain jobs (ex.: clown).
>Researchers have identified many things - like unpredictable laughter, pale skin, unkempt hair - that people tend to find unsettling in others. But they've also realized this: We humans are pretty poor judges of who we should trust, says psychologist Julia Shaw.

>We sometimes use terms that ascribe negative traits to people we don't know.
>"That guy is creepy."
>"What a weirdo."
>"She's freaking me out."

>But if we stop and think for a minute, what actually is creepiness? Do people know when they are creepy? Are you creepy?

>Until recently there was no science to help us understand creepiness. Then, in 2016, Francis McAndrew and Sara Koehnke of Knox College in Illinois published the first empirical study on the subject because they wanted to put their fingers on this elusive concept. They said that being "creeped out" is the result of an in-built threat detector - a detector that lets us know something is off by giving us feelings of confusion, unpleasantness, or just "the chills."

>But if creepiness is a threat detector, what is it warning us about?
https://ideas.ted.com/what-makes-a-person-creepy-and-what-purpose-do-our-creep-detectors-serve-a-psychologist-explains/