Why are clowns scary?

Children are frightened by clown-themed decor in hospitals, a survey suggests. How did the smiley circus entertainers become a horror staple? Anyone who has read Stephen King's It would probably never choose to decorate a children's ward with clowns. And it probably comes as no surprise to horror fans that a University of Sheffield study of 250 children for a report on hospital design suggests the children find clown motifs "frightening and unknowable". It is the fear of the mask, the fact that it doesn't change and is relentlessly comical Ramsey Campbell Clown images 'too scary' One might suspect that popular culture is to blame. In It, made into a television movie in 1990, Stephen King created a child-murdering monster that appeared as a demonic clown. King's It has sparked a slew of schlocky movies over the past 20 years, known as the killer clown or evil clown genre... BBC