Casting Director Says STD Testing Wipes Out Loads of Reality TV Wannabes

It’s the heyday of reality TV ... with fame-hungry hopefuls itching to hit our screens -- but one casting director tells us there’s no fast pass to fame if you can’t clear the ultimate requirement ... the STD test.

We caught up with Kristen Moss on TMZ Live Wednesday, and she broke it down -- if producers are tossing strangers in a house to explore each other sexually, they’ve gotta run heavy background checks ... and she says the big sensitive spot is STD testing, which wipes out a whole lotta hopefuls right off the bat!

Yup, you heard that right -- plenty of wannabes are actually riddled with STDs, which means they’re axed from casting ASAP ... especially since these shows pretty much guarantee things are gonna get hot and heavy beneath the sheets.

While Kristen isn’t behind casting "Love Island," she points to it as the perfect example -- the contestants basically have to be DTF -- and sure, some might find love, but let’s be real, it’s all about the fun, so they gotta pick the right people.

Catch the full clip ... 'cause Kristen also spills on how some red flags still manage to sneak past the casting stop sign -- just look at the contestants who got booted after their racist and homophobic posts resurfaced.