The teenage wannabe singer, who made it to the final three contestants alongside Johnny Ruffo and Andrew Wishart last week, said that he has been ordered by doctors not to sing or speak until tonight because of the vocal strain.
He told the Herald Sun: "I woke up on Friday and I went to say something and my voice completely went away and nothing came out. I had to go full monk and I didn't speak for two days let alone sing."
Mastin said that he has tried antibiotics and steroids and has also been taking drinking garlic, ginger and lemon in hot water to help speed up recovery. "We even tried steaming," he added.
Mastin has been the favourite to win The X Factor ever since judge Ronan Keating controversially told him to forget about his education and concentrate on his music career, but Mastin recently admitted that he doesn't want to be in pole position. "My biggest risk... is if people think I'm the favourite, they won't bother voting," he said.
The finalist is believed to be dating former fellow contestant Christina Parie, but she was eliminated from the competition three weeks ago.
> Australian 'X Factor's Andrew Wishart: 'I miss my family'
> Aussie 'X Factor' favourite Reece Mastin slammed by judges
Watch Reece Mastin singing on The X Factor below: