Getty Billy Bob Thornton is speaking out about his health and a rare condition he has that causes his him to have a restrictive diet. The 70-year-old Landman star opened up on Howie Mandel's podcast Howie Mandel Does Stuff about is "very restricted" diet. "Well, I'm allergic to wheat, dairy. I have type AB-negative blood, which is the rarest type in the world. It's, like, less than 1% of the population of the world has it," Billy Bob said.