'Kings of Pain' Star Adam Thorn Pukes After Bite from Venomous Lizard

"Kings of Pain" star Adam Thorn signed up to get bitten by a venomous lizard, and while he survived ... the pain was so unbearable he ended up vomiting.

Adam put his arm, and as it turns out his stomach, on the line for his History Channel show -- getting bitten on the arm by a Mexican beaded lizard. The critter has a venomous bite, but it hasn't been studied as much as its more famous relative, the Gila monster, making this a scary situation for Adam.

The guy's a real 'King of Pain' ... Adam's been bitten and stung by countless animals, and nearly strangled by a reticulated python, but this is the first time one of these encounters made him hurl.

Adam uses a 30-point pain index to rate his stings and bites ... and he's giving the Mexican beaded lizard a 26.5, which is higher than last season's 25.75 for the reticulated python.

The pain index includes intensity, duration and damage, and Adam experienced it all. The lizard's bite debilitated him so much, he couldn't handle the lizard when it came time for his co-star Rob Alleva's bite.