For those who are unaware of the latest trend to take social media by storm, 'perineum sunning' is here to toast the buns of the world's most health-conscious humans.
Popularised on Instagram by self-proclaimed "healer" and "ascension way-shower" Metaphysical Megan, 'perineum sunning' involves exposing the anus and genitals to the sun to experience a host of alleged health benefits.
Although Metaphysical Megan claims the pubic practice promotes better sleep, regulates the circadian rhythm and increases energy, others are not so convinced.
One adversary to ass-sunning is actor and Academy Award nominee, Josh Brolin.
The No Country for Old Men star took to Instagram on Saturday to share a strongly-worded message regarding the "ancient Taoist" technique.
"Tried this perineum sunning that I've been hearing about and my suggestion is do not do it as long as I did," Brolin wrote.
"My pucker hole is crazy burned and I was going to spend the day shopping with my family... instead I'm icing and using aloe and burn creams because of the severity of the pain.
"I don't know who the f**k thought of this stupid s**t but f**k you nonetheless. Seriously."
The 51-year-old finished his tirade with several hashtags, including "#assholecare", "#blackholefriday" and "#santamonicafiredepartment".
The post was accompanied with a picture of Metaphysical Megan exposing her bum to the sun, which she shared with her followers on October 22.
"For the past few weeks I have included sunning my bum and yoni [vagina] into my daily rising routine," she captioned the photo.
"Thirty seconds of sunlight on your butthole is the equivalent of a full day of sunlight with your clothes on... the intention is not to tan your butthole."
It appears Brolin did not adhere to Megan's recommendation.
A handful of doctors also appear less enthused with the wellness practice. Dr Diana Gall and chemist Shamir Patel told Insider there is no evidence perineum sunning has any health benefits and it's not worth increasing the risk of skin cancer.
"Practicing mindfulness comes in many different and safer forms, and there are no extra benefits of doing this naked in the sun," Dr Gall says.
