THE world’s scariest haunted house experience puts its guests through a psychological nightmare – shaving their heads and even allegedly waterboarding them.

McKamey Manor is run by Russ McKamey in San Diego, California, where a few participants every day are bound, slapped and even compelled to eat their own vomit.

There are around 24,000 on the waiting list for the experience which can last up to eight hours.

Guests are made to sign a waiver before they take part and McKamey insists on doing a background check to ensure those taking part do not have any serious medical conditions.

Despite this a guest suffered a heart attack during the experience in 2008, McKamey told The Guardian.

Special effects, animatronics, actors and live animals such as tarantulas, spiders and rats are used to send guests away shivering and crying.

McKamey films each volunteer to make a "mini movie" of each ordeal which are then posted on his YouTube channel which has nearly 39 million views.

Though he says he’s invested more than half a million dollars into the event, animal lover McKamey doesn't ask his guests for any money – just a dog food donation for Operation Greyhound.

He told Fox News: "It really is like watching somebody live their own horror movie right there, six inches in front of their face.”

While no one was ever lasted the full eight hours, McKamey says that in 2014 the record holder, known as Sarah P, lasted six hours inside the house before giving up.

Some of its most extreme moments occur on a morgue table, including the use of a live tarantula.

McKamey said: "You want to see true fear? You put live spiders crawling on somebody's face, and the tears are just flowing down their eyes in silence.

“It's like you're watching a silent movie.”

The fright fan says he does it "for the love of the haunt," simply wanting to put on the "biggest, craziest show" anyone's ever seen.

In 2016, Amy Milligan, of East County, San Diego, claimed she had been waterboarded at the haunted house – an allegation McKamey strongly denied.

She told the San Diego Union-Tribune that her head was repeatedly pushed under water while her hands were tied.

Milligan claimed that actors pushed her under the water again and again despite her begging for the experience to stop.

She said: “You give them so much trust and they just break it by waterboarding you and slapping you."

But McKamey denied those claims, telling the Union Tribune: “We do not waterboard, we do not even kind of waterboard.

“It’s psychological what we’re doing. They’re safe all the time.”

McKamey Manor was recently featured on an episode of Netflix series Dark Tourist.