There are some lessons in life we learn the hard way, but once we learn them, we learn them for good.
Take Vicks VapoRub - slather that on your chest for the first time and you might just find yourself feeling like you can breathe freely, your ailments soothed.
Given this boost, why wouldn't one go ahead and apply it to their balls? Well, just ask Jason Isaacs.
The Harry Potter actor made the terrible error as a child and the memory still haunts him until this day.
Asked about the worst injury he'd ever had on the Kermode on Film podcast, the 58-year-old said: "I'm thinking about the first time I remember hurting myself at all was when my best friend gave me some Vicks VapoRub when I had a bad chest when, you and I were at school together, I was 12.
"I rubbed it on my chest lying in my bed at night, where I sleep naked.
"And then I stroked myself the way one does, gently for comfort on the testicles – and I leapt out of bed, screamed, probably for my mother, I hope in retrospect that I didn't.
"I needed to wash the nether regions for quite a while before the stinging went away."
Hey, bet it stopped him thinking about his bad chest.
He added: "That's the first pain I remember. There have been many things since then, but that stays with me."
ALWAYS read the label folks.
Tessica Brown recently learnt this lesson the hard way, too. If her name doesn't ring a bell, how about Gorilla Glue Girl?
Yes, Tessica infamously tried using the heavy duty adhesive as hair glue and ended up in serious bother.
Her hair became savagely glued to her scalp for a month, with all of her DIY attempts to remove the product proving fruitless.
Mercifully, after her tale went viral, Dr Michael Obeng of MiKO Plastic Surgery in Beverly Hills offered to remove it free of charge, and Tessica flew out from Louisiana for the procedure last February.
Explaining how he did it, Dr Obeng told LADbible: "Basically what we did was use a solvent that broke it down without causing any injuries to the scalp. And that's what we did and it was very successful, and Tessica is recovering safely.
"The procedure took about two-and-a-half hours. After that, the team came and put more conditioner in her hair for another hour, and eventually she was taken to the recovery room where she spent another hour and then left and went to her hotel."
Featured Image Credit: AlamyTopics: Celebrity
Jake Massey