Blue cheese can give some people diarrhea but not everyone will get diarrhea when eating blue cheese.
Some peoples intestines act differently to dairy products including the blue cheese and may get diarrhea as a result of the blue cheese.
When you get diarrhea when eating cheese or blue cheese it's likely cause you're Lactose Intolerant and when you're Lactose Intolerant you'll usually also get stomach cramps and the diarrhea.
It's still safe to eat the cheese or dairy products when you're Lactose Intolerant but it just doesn't make you feel very good.
Blue cheese is safe to eat and will not make you sick when eating it.
The mold that blue cheese has is safe for people to eat unless you're allergic to that specific mold.
So blue cheese might make some people sick if they happen to be allergic to that blue cheese mold but for most people they eat the blue cheese without any health effects.
Blue cheese is also not very tasty for everyone so it might make you want to vomit or vomit when you try blue cheese for the first time and do not like it.
For example I cannot stand blue cheese but my mother she can eat blue cheese everyday if she wants too.
But for me I nearly vomited when trying to eat a piece of blue cheese that she had me try.
I can't stand the stuff but other people can.