Don’t believe everything you read—or everything you hear. Unverified but plausible-sounding rumors have been the basis for violent death and destruction throughout history, whether or not the stories had anything to do with the truth.

In their book A Colorful History of Popular Delusions, Robert Bartholomew and Peter Hassall describe rumors as “stories of perceived importance that lack substantiating evidence.” They also note that the sociologist Tamotsu Shibutani describes rumors as “improvised news,” which tends to spread when the demand for information exceeds supply. Such an information deficit most often occurs during wars and other crises, which might explain why some rumors have had such dramatic results. Here’s a selection of some of the most interesting rumors with real-life results collected in Bartholomew and Hassall’s book.

1. King Louis XV Was Kidnapping Children.

In 1750, children began disappearing from the streets of Paris. No one seemed to know why, and worried parents began rioting in the streets. In the midst of the panic, a rumor broke out that King Louis XV had become a leper and was kidnapping children so that he could bathe in their blood (at the time, bathing in the blood of children was thought by some to be an effective leprosy cure).

The rumor did have a tiny kernel of truth: Authorities were taking children away, but not to the king’s palace. A recently enacted series of ordinances designed to clear the streets of “undesirables” had led some policemen—who were paid per arrest—to overstep their authority and take any children they found on the streets to houses of detention. Fortunately, most were eventually reunited with their parents, and rumors of the king’s gruesome bathing rituals were put to rest.

2. London Was Going To Be Destroyed By An Earthquake.

Two small earthquakes struck London at the beginning of 1761, leading to rumors that the city was due for “the big one” on April 5, 1761. Supposedly, a psychic had predicted the catastrophe. Much of the populace grew so panicked that they fled town for the day, with those who couldn’t afford fancier lodgings camping out in the fields. One soldier was so convinced of the impending doom that he ran through the streets shouting news of London’s imminent destruction; sadly, he ended up in an insane asylum a few months later.

3. Jews Were Poisoning Wells.

Reports that Jews ritually sacrificed Christian children were not uncommon during the Middle Ages, but things took a particularly terrible turn during the spread of the Black Plague. In the 14th century, thousands of Jews were killed in response to rumors that Satan was protecting them from the plague in exchange for poisoning the wells of Christians. In 1321 in Guienne, France alone, an estimated 5000 Jews were burned alive for supposedly poisoning wells. Other communities expelled the Jews, or burned entire settlements to the ground. Brandenburg, Germany, even passed a law denouncing Jews for poisoning wells—which of course they weren't.

4. Brigands Were Terrorizing The French Countryside.

In July 1789, amid the widespread fear and instability on the eve of the French revolution, rumors spread that the anti-revolutionary nobility had planted brigands (robbers) to terrorize the peasants and steal their stores of food. Lights from furnaces, bonfires, and even the reflection of the setting sun were sometimes taken to be signs of brigands, with panic as the predictable result. Provincial towns and villages formed militias in response to the rumors, even though, as historian Georges Lefebvre put it, “the populace scared themselves.” In one typical incident, near Troyes on July 24, 1789, a group of brigands were supposedly spotted heading into some woods; an alarm was sounded and 3000 men gave chase. The “brigands” turned out to be a herd of cattle.

5. German-Americans Were Plotting Sneak Attacks on Canada.

Canada entered World War I in 1914, three years before the United States did. During the gap period, rumors circulated that German-Americans sympathetic to their country of origin were planning surprise attacks on Canada. One of the worst offenders of such rumor-mongering, according to authors Bartholomew and Hassall, was British consul-general Sir Courtenay Bennett, then stationed in New York. In the early months of 1915, Bennett made “several sensational claims about a plan in which as many as 80,000 well-armed, highly trained Germans who had been drilling in Niagara Falls and Buffalo, New York, were planning to invade Canada from northwestern New York state.” Bizarre as it may sound, there was so much anxiety and suspicion during the period that Canadian Prime Minister Sir Robert Borden requested a report on the story, which the Canadian police commissioner determined to be without any foundation whatsoever.

6. The Indonesian Government Was Hunting Heads For Construction Projects.

In certain parts of Indonesia, locals reportedly believe—or once did—that large-scale construction projects require human heads to keep the structures from crumbling. In 1937, one island was home to a spate of rumors saying that a tjoelik (government-sanctioned headhunter) was looking for a head to place near a local jetty construction project. Locals reported strange noises and sights, houses pelted with stones, and attacks from tjoelik wielding nooses or cowboy lassos. Similar rumors surfaced in 1979 in Indonesian Borneo, when government agents were supposedly seeking a head for a new bridge project, and in 1981 in Southern Borneo, when the government headhunters supposedly needed heads to stabilize malfunctioning equipment in nearby oil fields. Terrified townspeople began curtailing their activities so as not to be in public any longer than necessary, although the rumors eventually died down.

7. Powerful Aphrodisiac Gum Went On Sale In The Middle East.

In the mid-1990s, the Middle East was home to some alarming rumors about aphrodisiacal gum. In 1996 in Mansoura, Egypt, stories began spreading that students at the town’s university had purchased gum deliberately spiked with an aphrodisiac and were having orgies as a result. One local member of parliament said the gum had been distributed by the Israeli government as part of a plot to corrupt Egyptian youth. Mosque loudspeakers began warning people to avoid the gum, which was supposedly sold under the names “Aroma” or “Splay.” Authorities closed down some shops and made arrests, but never did find any tainted gum. Similar rumors cropped up the following year in the Gaza Strip, this time featuring a strawberry gum that turned women into prostitutes—supposedly, the better to convince them to become Shin Bet informants for the Israeli military.

8. Sorcerers Were Plaguing Indonesia.

In the fall of 1998, a sorcerer scare in East Java, Indonesia, resulted in the deaths of several villagers. The country was in crisis, and while protests raged in major cities, some in the rural area of Banyuwangi began agitating for restitution for past wrongs allegedly committed by sorcerers. The head of the local district ordered authorities to move the suspected sorcerers to a safe location, a process that included a check-in at the local police station. Unfortunately, villagers took the suspects’ visits to police stations as proof of their sorcery and began killing them. Anthropologists who studied the incident said the stories of supposed sorcery—making neighbors fall sick, etc.—were based entirely on rumor and gossip.

9. Obama Was Injured By A White House Explosion.

The @AP Twitter account has been suspended after it was hacked. The tweet about an attack on the White House was false. — AP Stylebook (@APStylebook) April 23, 2013

These days, rumors have advanced technology to help them travel. On April 23, 2013, a fake tweet from a hacked Associated Press account claimed that explosions at the White House had injured Barack Obama. That lone tweet caused instability on world financial markets, and the Standard and Poor’s 500 Index lost $130 billion in a short period. Fortunately, it quickly recovered. (Eagle-eyed journalists were suspicious of the tweet from the beginning, since it didn’t follow AP style of referring to the president with his title and capitalizing the word breaking.)

A version of this story ran in 2015 and was republished in 2019.