We’ve all heard them—those bits of “common sense” passed down from parents, teachers, and well-meaning adults. But a surprising number of these beliefs about the human body just don’t hold up to science.
Here are 10 long-standing myths you can officially stop believing.
1. We Only Use 10% of Our Brain
This one is completely false. Brain imaging studies show that we use nearly all parts of our brain, just not all at once.
Different regions handle different tasks—movement, memory, emotion, problem-solving—and even during sleep, the brain remains highly active. The “10%” idea is more myth than science.
2. Shaving Makes Hair Grow Back Thicker and Darker
Shaving doesn’t change hair thickness, color, or growth rate.
What does happen is visual: shaved hair grows back with a blunt edge instead of a natural taper, which can make it feel coarser and look darker at first.
3. Gum Stays in Your Stomach for Years
Nope. While gum isn’t fully digestible, it doesn’t stick around for years.
It moves through your digestive system like other indigestible materials and is typically passed within a few days.
4. Cracking Your Knuckles Causes Arthritis
There’s no solid evidence linking knuckle cracking to arthritis.
The popping sound comes from gas bubbles forming and collapsing in joint fluid. While excessive cracking might cause temporary irritation for some people, it hasn’t been shown to cause long-term joint damage.
5. Going Outside With Wet Hair Makes You Sick
Colds are caused by viruses—not temperature or damp hair.
That said, cold weather may slightly affect immune response or behavior (like spending more time indoors), but wet hair itself doesn’t cause illness.
6. Sugar Makes Kids Hyperactive
This one is more complicated than people think.
Most controlled studies show no consistent link between sugar and hyperactivity. However, parents often perceive increased energy—especially in exciting settings like parties.
Sugar can still affect mood and energy levels, but it’s not the guaranteed hyperactivity trigger it’s often made out to be.
7. Touching Frogs or Toads Gives You Warts
Warts are caused by the human papillomavirus (HPV)—not amphibians.
Frogs and toads can have bumpy skin that looks like warts, which likely sparked the myth. Some species can secrete mild toxins, but they won’t give you warts.
8. You Must Wait an Hour After Eating Before Swimming
There’s no strict rule here.
After eating, your body directs more blood flow to digestion, which might make intense activity uncomfortable—but it won’t suddenly cause dangerous cramps or drowning.
Swimming after a light meal is generally fine.
9. Rusty Nails Cause Tetanus
Rust itself doesn’t cause tetanus.
Tetanus comes from the bacterium Clostridium tetani, which lives in soil, dust, and manure. Rusty nails are risky because they’re often found in environments where the bacteria thrive—and puncture wounds can introduce it into the body.
Bottom line: it’s the bacteria, not the rust—but vaccination is crucial.
10. You Can Easily Catch Diseases From a Toilet Seat
It’s highly unlikely.
Most disease-causing organisms don’t survive long on toilet seats, and transmission usually requires direct contact with infected bodily fluids. You’re far more likely to pick up germs from door handles, phones, or shared surfaces.
Still—washing your hands is always a good idea.
