When I was little, I saw these commercials on TV about how "sniffing" is bad for you and kills brain cells. I thought it meant that when you have to blow your nose if you don't blow it, but sniff it in instead, then that kills your brain cells. So for years I wouldn't sniff in whenever I had a runny nose. The commercials went off the air for a few years and it wasn't until the end of high school when they re-aired them did I realize that it was referring to sniffing drugs/chemicals and not sniffing snot.
A childhood belief about adverts

others believed things like this
- My brother used to tell me if I picked my nose I would become more stupid because bogey were brain cellsAnon
- I used to think that if you didn't blow your nose and just sniffed the snot up, you head would blow up.Anon
- i was always told if i picked my nose my brain would fall out! i belived it for years!Anon
- I thought if i picked my nose too many times, my head would blow up.— i m a moron
- i used to believe that if you picked
your nose your brain would cave in...— mr bogtrotter - when i was little my mum used to tell me if i picked my nose too much my brain would fall out!!! think it did— Maz