Lead paint in kids' rooms. Smoking. Flammable pajamas. It's easy to name items that are more dangerous than we realized. But some things people once considered dangerous aren't harmful at all. 

1. Dancing

Safety dance? More like deadly dance. In its 1926 article “Death of Girl, 17, Laid to Charleston Dance,” The Washington Post reported on a girl who perished after dancing the Charleston. The paper interviewed the girl's doctor, who blamed her death on the “extreme physical exercise” of this classic dance move, which he said was “particularly dangerous for young women.” 

But potential “inflammation of the peritoneum” wasn't the only thing to be concerned about when flitting across the dance floor. Even the most traditional of dances could do serious damage and lead to all sorts of evil. “The high kick, displaying bare legs and arms of our little girls in the presence of even small boys, cannot honestly be said to tend to beget in those children the highest sense of modesty, purity so greatly prized in our women,” a Dr. Waldron told a local ministerial association in 1925; his remarks were quoted in  The Pittsburgh Courier article “Flays Teaching of Dancing in Public School: ‘Display of Bare Legs is Hurtful’” [PDF]. “The folk dances become the way and door to the dancing school; the dancing school is the feeder to the dance hall and public ball room and these inturn [sic], load to the brothel,” the doctor said. “Statistics show from one-third to two-thirds of the prostitutes in our large cities come from the public dance halls and ballrooms.” 

While few are currently concerned about the risk of death by dancing, there are still associations between promiscuity and certain dance styles. Some schools have rigid rules about what's allowed at school dances—especially when it comes to the distance between partners—and other towns have gone full Footloose, outlawing dancing all together, either for religious reasons, the crime rate at nightclubs, or like one town in Wisconsin, for just a short-lived promotional stunt

2. Competitive Sports (for Girls)

According to 1920s wisdom, if a girl wants to stay desirable and get married, she must refrain from practicing competitive sports. “Too many athletics threaten to rob girls of their chief appeal to men,” warns a Victoria college headmistress in “Says Athletics Harm Girls: English Woman Warns Students Not to Lose Appeal to Men,” an article published in The Washington Post in 1922. “The modern girl is trying to do too much at football,” she continues. “Her charm, balance and poise will all be lost, and her dignity lowered if she endeavors to emulate man too closely.”

Worse still, if she participated in sports in high school, she risked wearing herself out, ruining her chances for future happiness. “Must I continue through my life half enjoying living just because I gave too much of myself to competitive sports, to win a few medals which lie unnoticed and tarnished in a box?” asks a married woman in the 1931 Chicago Daily Tribune article “Competitive Sports are Dangerous for High School Girls.”  

It wasn’t until World War II that women’s competitive sports gained greater acceptance. After women proved their strength by joining the workforce or enrolling in military service, “organizations for women in sport began to increase as sport became more competitive and intercollegiate and interscholastic competition spread.” The Civil Rights movement in conjunction with Second Wave feminism also aided in the growing presence of women’s competitive sports.

3. Licking Stamps

Back in 1916—when snail mail was the norm, and before stamps evolved into stickers—The New York Times warned against the dangers of stamp licking. “Aside from hygienic reasons, it is dangerous to lick postage stamps on the ground that the stamps are bacteria-laden and under favorable conditions might easily convey pathogenic types especially colon, diphtheria, and tubercle bacilli,” said the Philadelphia scientists who conducted the study. 

A mere four years later, J. Diner and G. Horstman—two members of the American Pharmaceutical Association—disproved this theory. A 1920 article in The Boston Daily Globe quoted the study originally printed in American Medicine, saying, “The hygienic reason that people should not lick postage stamps is certainly sound. Nevertheless this practice is scarcely to be construed as a potential danger compared with eating and drinking which are so essential for sustenance but are responsible for a large measure of bacteriological contamination of the oral cavity.”

On that note, Seinfeld fans may wonder whether Susan could have actually died by licking all those cheap wedding invitation envelopes. Thomas P. Connelly, D.D.S., says no. “In general terms, most envelope glue is produced from gum arabic, which comes from tree sap,” he explains in a piece for The Huffington Post in 2011. “It is safe for humans and is also used in some other things we eat (M&Ms, gumdrops, etc.). The glue can also be more petroleum-based, as we can see by this answer from someone in the UK post office. But either way, it would appear that the glue is indeed safe. This goes the same if you ingest it, or if you cut your tongue while licking.”

4. The Color Purple

In the early 1900s, an interior decorator would never choose the color purple. A Boston Globe article from 1903—titled “Dangerous Tints: Some Colors Will Drive a Person Mad if the Eyes Are Continually Looking at Them”—called it "the most dangerous color there is":

If purple walls and a red tinted window surrounded you for a month with no color but purple around you, by the end of that time you would be a mad-man. No matter how strong your brain might be it would not stand the strain, and it is doubtful if you would ever recover your reason.

That wasn't the only color to avoid. Scarlet could push you into a murderous rage, while blue “excites the imagination and gives a craving for music and stagecraft, but it has a reaction that wrecks the nerves.” Meanwhile, “Solitary confinement in a yellow cell … will weaken any system and produce chronic hysteria,” and “sheer dead white, unbroken, will destroy your eyesight.”

But according to color expert Kate Smith, purple has the power to calm the nerves, improve the mood, and even inspire creativity. Why else would Harold choose a purple crayon? 

5. Dungeons and Dragons

D&D came under fire in the 1980s when suicides and murders were loosely linked to the game. A few years ago, Mental_Floss compiled a list of complaints against the fantasy role-playing game, including ones that mention cults, witchcraft, Satan, and murder. 

One mother was concerned by the amount of time and attention her kids and their friends devoted to the game. “They're always planning what they will do the next time. Kids have lost jobs, flunked out of school. They totally confuse reality and fantasy," she said. "It (the game) becomes their god."

6. Hanging onto Straps on Public Transportation

Ladies feeling under the weather in 1912 could blame public transportation. Not because there were germs lingering on the poles, or floating through the crowded street car, but because holding on to the straps—now replaced with rods—was “a frightful strain upon [your] internal organs,” according to the unnamed but "prominent" physician interviewed in 1912 for the Chicago Daily Tribune‘s “Strap Hanging Dangerous for Women.” According to the physician, "Women do not have the strong shoulder muscles that men possess, and while men use only their arm and shoulder muscles to steady themselves, women are obliged to use all the muscles in their bodies for the same purpose.” 

Lillian Russell, the author of the piece, even made it a political issue, saying, “It is high time that women were granted the rights of suffrage, for without suffrage they have neither seats in the cars nor the votes to protect themselves against such a horde of so-called men.”

Hanging on straps might no longer be considered dangerous for ladies, but seating on public transportation can still be a contentious and gendered issue. At least there are taxis.   

7. Where's Waldo? and other children's books

It’s hard to find Waldo among the crowded pages of a Where’s Waldo? book, let alone notice every detail hidden among the illustration. But once a kid in Long Island found a woman’s partially exposed breast on the beach page in the first book of the series, chaos—in the form of overly-concerned parents—ensued. The woman's breast, described as “about the size of the lead tip of a pencil,” caused the book to be banned from that town's school library in 1993. Other children’s books that have been pulled from the shelves include A. A. Milne’s Winnie the Pooh, Sylvester and the Magic Pebble by William Steig, and—in an unfortunate mix upBrown Bear, Brown Bear, What Do You See? by Bill Martin Jr.

8. Gum

Your mother might have told you never to swallow your gum because it would stick in your gut for 7 years. That might be a good way to scare a child into throwing their chewed gum in the trash, but this claim is entirely false. Yes, the gum isn’t broken down like other food, but it’ll still pass through your digestive system at a normal rate. That being said, it’s still not a great thing to do.

9. Sitting Too Close to the TV

Before TVs had flat screens, hundreds of channels, and crystal clear imaging, they were clunky and emitted radiation that could potentially worsen the viewer’s eyesight after prolonged exposure. However, in 1967, a “factory error” caused some defective General Electric televisions to emit 10 to 100,000 times the amount of radiation health officials deemed acceptable. GE recalled the TVs and updated their new models with a leaded glass shield surrounding the tubes inside the television to solve the problem.

Radiation isn’t something to worry about anymore, but you can still strain your eyes if you spend too much time staring at a screen—so with our iPhones and our computers and all of our other devices, television is the least of our problems. 

10. The Tomato

Paired with the wrong platter, a tomato had the power to kill. When European aristocrats became sick and died after eating tomatoes, the fruit was dubbed the “poison apple.” It was later discovered that the tomato itself wasn't deadly—but its high acidity caused it to “leach lead” from the pewter plate, resulting in lead poisoning. But the tomato’s reputation was set.

The tomato’s sad tale continued when the Green Tomato Worm invaded tomato patches across New York in the 1830s. Personal accounts of encounters with the worms resulted in rumors about how poisonous they were. It was believed that Ralph Waldo Emerson thought they were “an object of much terror, it being currently regarded as poisonous and imparting a poisonous quality to the fruit if it should chance to crawl upon it." The worm turned out to be totally harmless, people’s fears eventually subsided—and the tomato became a garden and salad staple.

11. Tea

In the 19th century, if an Irish peasant woman were drinking tea, it meant something else was being put on the back burner—something far more important, like her domestic duties. According to Dr. Helen O’Connell, a lecturer at Durham University, and author of “'A Raking Pot of Tea’: Consumption and Excess in Early Nineteenth Century Ireland,” published in Literature and History journal, “Drinking tea was thought to threaten traditional ways.” A tea break among women could lead to them plotting a rebellion or engaging in political discussion, and publicly distributed pamphlets warned against the dangers of the drink. Now we just consider it a nice alternative to coffee, which was also once considered dangerous

12. Clothes

“If the doctors are to be believed, the wearing of clothes is more dangerous to human life than their utter absence would be,” wrote the authors of the 1901 Boston Daily Globe article “Don’t Wear Clothes: That is, if You Would be Entirely Healthy…"  The British doctors who were consulted for the piece advised against wearing cotton and linen as well as garters and waistcoats, which they argued “are a permanent menace to life and health.”

Their reasoning is partially accurate—the body does breathe through both the lungs and the skin (despite what all of those internet myth sites will tell you), and there are some fabrics that are less “breathable” than others—but “nonporous clothing” isn’t quite as “disastrous” as they seem to have thought. 

Today, we know that cotton is one of the better fabric options available to us; some synthetic materials can cause rashes and skin irritation. However, there have been recent articles about the danger of some clothes—not because their “clammy surface ... imparts any variety of cold, up to and including pneumonia,” but because some dyes include toxins as a result of polluted water near the factories [PDF].

13. Writing Letters

Just a glance at a person's tweets, blog posts, and status updates can be enough to tell you everything there is to know about their problems. But oversharing isn’t a new epidemic caused by the Internet. In 1898, Amelia E. Barr wrote a chapter called “Dangerous Letter Writing” in her book Maids Wives and Bachelors in which she said “Young women are proverbially fond of playing with edged tools ... And of all such dangerous playthings a habit of promiscuous, careless letter-writing is the worst; for in most cases the danger is not obvious at the time, and the writer may even have forgotten her imprudence when she has to meet the consequences.” Barr credits cheaper postage for the impulsive way girls wrote overly sentimental letters and sent them off immediately.

In a highly prescient passage, she writes,

The abuse of letter-writing is one of the greatest trials of the epoch ... Every one cries out, and insists upon your listening. They write events while they are only happening. People unknown intrude upon your time and take possession of it. Enmities and friendships thousands of miles away scold or caress … For a mere nothing—a yes, or a no—idle, gushing people fire off continual notes and insist upon answers.

Letter writing may no longer be considered dangerous, but thanks to cell phones, computers, and all other communication enabled gadgetry, it's definitely still a nuisance. 

14. Public Toilets

Are you a hoverer or a toilet seat cover user? There's very little need to be putting in that extra effort when using a public restroom, because despite what you might have heard, it's impossible to contract a sexually transmitted disease just by sitting on a toilet. 

Donald G. McNeil Jr., a science and health reporter at The New York Times, attributes the fear of contracting a venereal disease from the toilet seat to an age old excuse. In response to a reader's question about the dangers of toilet seats, he explained that the STD myth was probably a result of cheating partners refusing to admit their infidelity when their partners angrily ask them about why he or she "suddenly has symptoms of syphilis, gonorrhea, pubic lice, or any other unpleasantry." Instead of coming clean, the unfaithful partner can easily say “I have no idea, dear—I must have gotten it from a toilet seat..." and then move on without an argument. 

Non-sexually transmitted diseases like various flesh-eating bacteria, the norovirus, or E. Coli are carried through vomit or feces, both of which are visible and thus avoidable. And far as other germs go, as long as the skin on your rear end and thighs is fully intact—thick skin works as a barrier—there's almost nothing to be worried about. 

That's not to say that there aren't germs on a toilet seat—in fact, there's an average of 50 bacteria per square inch on one's surface—but compared to a cutting board, a kitchen sponge, or your cell phone, toilet seats are cleaner. Just something to think about the next time you stick your iPhone next to your pillow. 

15. Air conditioning

The invention and subsequent increase in accessibility and affordability of air conditioning in the 1920s and '30s brought a general sigh of relief to homeowners and office workers used to sweating through the summer months. But in Washington D.C., some government officials didn’t give the new technological addition to the Senate chamber such a warm welcome. In May 1929, John E. Rankin, a Democrat from Mississippi, filed a complaint about the chilly air temperature in the chamber, saying, "This is regular Republican atmosphere, and it is enough to kill anybody if it continues." 

Rankin was wrong. In fact, according to a 2013 study, since 1960, air conditioning has cut heat-related deaths by 80 percent. "The likelihood of a premature death on an extremely hot day between 1929 and 1959 was 2.5 percent," and has since dropped to less than 0.5 percent.