Before the internet, medical knowledge traveled by jungle gym.
It came from the kid at recess who could burp the alphabet and told you that gum stays in your stomach for seven years. He said cracking your knuckles will give you arthritis, and that swimming after eating a hot dog will make you cramp and sink like an anchor. No citations, no evidence, just terrifying confidence and a Kool-Aid mustache.
Adults weren’t much better. Parents, guardians, teachers, camp counselors and older siblings all contributed to the grand public-health curriculum of the 1970s, ’80s and ’90s: Going outside with wet hair gives you a cold. Cross your eyes, and they might stay that way forever.
“That was just how people learned things about their bodies,” says Dr. Aaron E. Carroll, coauthor of Don’t Swallow Your Gum!: Myths, Half-Truths, and Outright Lies About Your Body and Health. “You couldn’t Google a claim. You asked your mom, who heard it from her mom, who heard it from a doctor she trusted decades earlier.”
So we rounded up the most persistent medical myths that circulated through childhood, and asked doctors and scientists what everyone got wrong.
Wet hair in the winter causes colds
Apparently, every damp-headed kid was one chilly breeze away from coming down with something. But colds aren’t caused by wet hair, frigid air or your mother’s disapproval. “Colds are caused by viruses, not the weather,” says Dr. William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee.
The confusion, Schaffner says, comes from timing. Respiratory viruses spread heavily in winter, which is why we call them “colds” in the first place. But damp hair doesn’t make you more likely to encounter a virus or get sick from one.
We spent our childhoods believing that swallowed gum was basically a nonrefundable deposit in our intestines.
Peter Arkle
Cracking your knuckles causes arthritis
For generations, knuckle-cracking was another step toward hands shaped like tree roots.
Then came Dr. Donald Unger, who for more than 60 years cracked the knuckles of his left hand at least twice a day while leaving his right hand alone. That added up to at least 36,500 cracks. In 1998, he published the results: X-rays showed no arthritis and no difference between the two hands. His work later won an Ig Nobel Prize for oddball research.
So what is that satisfying sound? According to Dr. Richard S. Gilbert, a hand and wrist surgeon at Northwell Health in Great Neck, New York, it’s “a mechanical process.” When you stretch a joint, he explains, “the pressure within the joint decreases,” creating a small vacuum that pulls dissolved nitrogen gas out of the synovial fluid, the lubricant that keeps joints moving smoothly. “Tiny bubbles form and then collapse,” he says, producing the familiar pop.
The important part is that the collapsing bubbles don’t damage the joint or cartilage. “Cracking knuckles does not result in arthritis,” Gilbert says.
Swimming after eating causes cramps and drowning
This was the sacred pool rule: Eat one hot dog, three chips and half a grape soda, and you were sentenced to an hour on a towel, watching luckier children enjoy their freedom. Because swimming too soon after eating could cause your stomach to cramp so much that you’d sink before the lifeguard finished rotating his whistle.
Carroll suspects the rule had less to do with physiology than with crowd control. “A lot of these rules started out as practical adult management dressed up in the language of safety,” he says. “‘Wait an hour’ is a lot easier to enforce than ‘I need a break from watching you in the pool.’”
The danger calculation also favored the myth. “Nobody is going to demand a randomized controlled trial when they think a kid’s life is on the line,” Carroll says. If the rule is wrong, the worst outcome is whining. If it’s right, the fear is tragedy. That makes parents enforce it, repeat it and judge anyone who doesn’t.
However, “There are no documented cases of drownings caused by swimming after eating,” Carroll says.