Billy Bob Thornton Details Allergies, Rare Blood Type Behind Extreme Diet

Billy Bob Thornton opened up about his lifelong health struggles and the extreme diet they demand.

The 70-year-old actor shared details during a recent episode of the "Howie Mandel Does Stuff" podcast. "My diet's very restricted. 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," he said. "It means you have less digestive enzymes. That's one of the things that goes along with it. But I just grew up with a lot of allergies."

Thornton listed more restrictions: no dairy, wheat, shellfish or meat such as pork or beef.

He described his breakfast that morning as a bowl of blueberries. Later, he planned gluten-free chips with dairy-free cream cheese. "When I was a kid, you know, I grew up in Arkansas and East Texas and I ate everything," he said. "I just assumed everybody felt like s--- after they ate. I didn't know."

His limits led to unusual snacks. Before a "Landman" Q&A event, Thornton scanned the green room for safe options amid deli meats, cheeses and crackers. He spotted grapes but wanted more. "OK, so I'll be bored as hell with this," he thought.

Then he tried something new. "I dipped this grape in the Dijon mustard," he said. "It was one of the best things I ever had in my lifetime. So now it's become a thing for me."

Thornton once transformed his body for roles but has stopped. In a January appearance on "Late Night with Seth Meyers," he said he quit because "it does not feel good."

He gained 60 pounds for "Tombstone" and "U Turn" in the late 1990s, then dropped to 128 pounds for "Pushing Tin." "It’s funny — if I ever see a picture of those days, because this is back … when you’re a younger actor, you’re like, ‘Well, I’m going to gain 75 pounds for this, and the next time I’m going to do this,’ and whatever, ‘I’ll cut my own cheek,’ you know, that kind of thing," he said with a laugh. "After a while, as you get older, you stop doing that stuff."

Thornton stars in the Paramount+ series "Landman" with Ali Larter, Demi Moore and Sam Elliott. The show follows roughnecks and billionaires in West Texas chasing oil riches.

"I think the thing that I learned that I wasn't quite aware of before — because I knew some about the oil business — but I knew people more on the sort of suit side of it, you know, in Texas," he told Fox News Digital in November 2025. "One of the things that surprised me was how many people who had had broken lives are working in the oil fields. Got ex-cons and all kinds of things working out there because they can make from $120,000 to $180,000 a year to take care of their families when they try to straighten their lives out."