Brooks, who has been open about dealing with anxiety, took to social media Monday to address what happened.
"I'd like to address what happened yesterday," he wrote. "I woke up, and did my typical routine of morning vomiting. It didn't go away like it normally does, but I figured it would calm down once I got to the stadium. It did, but I felt exhausted. The nausea came back, and I tried to battle through it and went out for the first drive. The nausea and vomiting came back until I left the field, and tried everything I could to get back for my teammates but just wasn't able to do it.
"Make no mistake, I'm NOT ashamed or embarrassed by this nor what I go through daily. I've had this under control for a couple of years, and had a set back yesterday. The only thing I'm upset about is that when my team needed me, I wasn't able to be out there with and for them. Lastly, I appreciate the support of my coaches, teammates and fans. It doesn't go unnoticed."
Brooks has missed five games during his career as a result of anxiety-related illness. Before Sunday, the most recent absences came in 2016, when he missed two games in three weeks. It was then that he really began to try to get to the root of the issue. He was diagnosed with an anxiety condition and began to take proactive measures, including seeing a psychologist once a week. He went a full two-plus seasons without missing a game.
Brooks has been helped by his friendship with right tackle Lane Johnson, who missed Sunday's game with a concussion. Johnson also deals with anxiety. The two have shared that they'll often vomit at the same time pregame, and text each other to joke about it.
"This is not a football issue with Brandon; this is a real-life issue that he has come out and publicly acknowledged and kind of shared his story a few years back," coach Doug Pederson said during a radio appearance on 94.1 WIP on Monday. "It's something that he's dealing with each and every day of his life. You never really know what triggers it. We're here to support him. We love him. It is unfortunate that it happened, but it's something that he deals with every single day. We're just going to continue to support him."
Brooks, a 2012 third-round pick of the Houston Texans, has developed into one of the best linemen in football since joining the Eagles in free agency in 2016.
The Eagles made him the highest-paid guard in the NFL by signing him to a four-year extension in November that is worth $56.5 million and contains $30 million in guarantees. The deal runs through 2024 for the 30-year-old Brooks, who is in the midst of arguably his best season as a pro despite coming off an Achilles rupture suffered last January in a playoff loss to the New Orleans Saints.