Read the article at: https://www.vice.com/en_asia/article/kbvk5m/we-asked-scientists-why-clowns-freak-us-the-hell-out-id

The whole clown getup—the exaggerated features, the colorful face paint, the red nose—doesn’t help either. “The clown face violates the normal parameters of what we are programmed to recognize in a safe facial expression,” says Bruce Cameron, a licensed counselor in Dallas who has treated several patients with coulrophobia. “The experience is disturbing or shocking because the brain now has to take extra steps to decode the meaning of the face to discern if it is friendly or hostile. The makeup makes it harder to recognize emotions or intent.”