The Lyric Opera of Chicago was holding a dress rehearsal Monday of "Die Meistersinger von Nurnberg" when the incident occurred during the third act, the Chicago Tribune reported.
During a scene involving carnival performers, Wesley Daniel came out on stage on stilts with fire breathing equipment, the Chicago Sun-Times reported.
"He blew one or two fireballs, and then it looked like he had spilled it on his chin or his chest or something," said Jason Wambsgans, a Tribune photographer who was on hand to shoot the dress rehearsal.
"It kind of consumed him, and he was staggering across the stage and then fell off his stilts on the opposite side of the stage," Wambsgans added.
Paramedics transported Daniel to Loyola University Medical Center in critical condition with second-degree burns to his face and throat, the Chicago Fire Department said.
The Lyric Opera said it would no longer include fire breathing in the carnival scene of "Die Meistersinger von Nurnberg."