When I was little, we visited a neighbor and I was checking out the Sweet & Low packets on the table. Mom told me not to touch those. Why? "Because they cause cancer."
I assumed this was the actual purpose of Sweet & Low, like it was some kind of suicide pill. Needless to say, I thought the neighbors were pretty scary for keeping cancer poison attractively displayed right on the table.
A childhood belief about sweeties

others believed things like this
- My mom told me if I picked my nose, I would get cancer.— xxXSaraXxx
- My sisters once told me if I blinked too much I would get cancer.
How mean... D:— Budster - My Gran told me that if I picked my nose, I´d get brain cancer. Traumatised? Yes I was!— Windy Girl
- I thought you always die if you A. get cancer or B. have a heart attack— Nate
- Mom told us that if we didn't eat every single bite of our veggies at dinner time, we'd get colon cancer.Anon
- when i was little i thought people with big heads or big noses had cancer...Anon