Not Romance! What's the most embarrassing question

What's the most important, embarrassing question you dared to ask?

On Facebook, Craig Conn's list of things he would not ask prompted a moment of candour from me.

Some questions may be embarrassing, but you really do need to ask. Your life or lifestyle might depend on it. I firmly believe that my mother got C-Difficile, and almost died, from a medical professional. Those white coats aren't necessarily as clean as they look.

Embarrassing questions I've asked to the surgeon: "Do you have AIDS?" (He was offended that I should think of asking)

To my husband's doctor's assistant, "Aren't you going to wash your hands before touching my husband?" Got three demonstrations of handwashing after that, which didn't help much because he wiped his nose on his fingers six times and his hands on his jeans (thigh, high up) three times.

To a former boyfriend: What are those white zits around your mouth? Have you been tested for herpes?

If you haven't asked anyone anything truly cringe-making, what do you wish you'd asked? What will you ask, next time?