Eating a spoonful of sugar will cure your hiccups. Picking up a toad will give you warts. These little dubious tips are commonly called old wives' tales -- you usually hear them from your superstitious grandparents, and they're usually bullshit.
Usually, but not always. Some of these folk cures and bizarre warnings have stuck around for a reason, and it just took science a while to catch up ...
5Yes, Peanut Butter Gets Gum Out of Hair
So you were chewing gum and for whatever reason decided to store it for later by sticking it onto your scalp. We have no idea why techniques for getting gum out of hair became necessary, let alone popular, seeing as there are very few reasons why gum should ever come into the vicinity of the top of your head (maybe you were aiming for your mouth and missed?). Regardless, there are plenty of folk remedies that claim to hold the solution to this apparently age-old problem, and one of the most popular is to shampoo your gummed-up head with peanut butter -- the offending wad will wash right out.
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For those who doubted that good grooming and kinky food fetish play could go together, there's your proof.
Honestly, it sounds like a prank. Wasn't there a whole Simpsons subplot about this going disastrously wrong?
It seems like such a nonsense answer because, well, gum is sticky, and peanut butter is sticky, so how would this not just create a bigger, stickier mess? And one that makes it look like somebody took a shit on your head? The secret, though, is the oil.
Michael Saechang, via Wikipedia
Meaning if there's no PB&J around, you could probably improvise.
Basically, the reason gum doesn't come out with a quick shower is that it's a hydrophobic substance -- it doesn't dissolve in water. Try to wash that shit out and it will only stick harder, like an alien facehugger poked with a scalpel. But it does dissolve in oil, and peanut butter is full of it.
"Wait, doesn't that mean I could use cooking oil or some shit instead?" Sure, and you can browse YouTube and watch thousands of videos of people using olive oil -- it seems to work fine. People always cite peanut butter either because it's easier to work with (as opposed to leaning over the sink and dumping half a bottle of canola oil on your head) or because it makes a more interesting "fun fact" since it's so unexpected. Hell, that's why we did it.