He then took to Instagram to issue a warning, to save other people from making the same mistake.

"Tried this perineum sunning that Ive been hearing about and my suggestion is DO NOT do it as long as I did," he wrote. "My pucker hole is crazy burned and I was going to spend the day shopping with my family and instead Im icing and using aloe and burn creams because of the severity of the pain. I dont know who the fuck thought of this stupid shit but fuck you nonetheless. Seriously."

"Perineum sunning" has been circulating online for a while now, originating with a post by Instagram "healer" Metaphysical Meagan, who wrote at length about the benefits of exposing your rear end to the sun. She claimed that just 30 seconds of bum-sunning per day could help regulate your sleep, boost your libido, improve focus, and increase creativity.

Medical professionals, however, have advised against the "ancient Taoist practice," as repeated or prolonged exposure to sunlight can cause serious skin damage to which Brolin can certainly attest.

"Practicing mindfulness comes in many different and safer forms, and there are no extra benefits of doing this naked in the sun," said Dr Diana Gall .