When I had an itch as a child I thought that it was caused by a little creature inside me that wanted attention. Kind of like a cat that wants petted will rub against your leg, the creature would rub up against the inside of my skin until I had scratched it enough, then it would go off on its merry way.
Also, my dad used to tell me that if you sneezed 16 times in a row you would die. Not that big a deal unless you have allergies, which I do. I remember quite a few times as a kid where I reached 15 sneezes and then nearly blew my eardrums out trying to hold in deadly number 16. :)
A childhood belief about general

others believed things like this
- I used to believe that ants walked inside your body and that's what caused an itch.Anon
- I believed that the inside of a tomato was a small, living creature and I flatly refused to eat that bit.Anon
- that sneezes were caused by little pixies crawling up your nose and brushing past your nose hairs— Joanna
- i thought that you had like a box or something inside you to hold your soul for the longest time— jill
- i used to believe that when i had an itch or a tickle, it was because there were ants crawling beneath my skin— Willa
- I used to think that "One, two, three times a lady"
was: "one, two, three times related"Anon