My dad was always told that if you bite your fingernails, you'll blow up like a balloon. This was "confirmed" by his dad whenever a pregnant lady walked by. Grandpa would point and say, "see, she bites her fingernails." needless to say he never bit them.
A childhood belief about biting my nails

others believed things like this
- I used to believe that I would get worms if I bit my fingernails. — Leslie
- My Mom used to tell us that if you bit your fingernails, they would cut a hole in your stomach.— Linda B
- i used to believe that if i bit my fingernails then a finger would grow in my stomach— polly
- my grandpa told me if you pick your nose too far then a snail will bite your finger off haAnon
- My sister told me once that if I sucked too much helium out of a balloon, my lungs would explode.Anon
- I used to think that if you didn't blow your nose and just sniffed the snot up, you head would blow up.Anon