Belgian Coca-Cola Scare
When 100 students fell ill after reportedly drinking Coca-Cola, thousands of people stopped drinking the soda and some countries even temporarily banned its sale over fears of contamination. Subsequent investigations found that some of the drink did contain some harmful ingredients but that the vast majority of those who had become ill were simply suffering from a mass psychogenic illness.
In 1994, several medical staff that were treating Gloria Ramirez, a woman suffering from cervical cancer, began to faint and collapse. Obviously, this led to reports that the ill woman was actually toxic and giving off poisonous fumes or spreading a disease. More nurses soon began to apparently suffer from the effects and any person who had encountered her were isolated. An investigation from the Health Department found that none of the medical staff had anything wrong with them and had simply suffered from a mass delusion.