Bryan Johnson, a biohacker who has spent millions on procedures to reverse the aging process, recently experienced a terrifying side effect from his latest experimental treatment. The 47-year-old tech entrepreneur revealed that his face swelled alarmingly and he suffered blurred vision following an injection meant to restore youthful volume by stimulating natural fat growth.

Johnson, who has spent nearly $2 million on his anti-aging regimen, combines strict diet and exercise with controversial therapies, including using his own son’s blood. His recent treatment involved injecting a fat-derived extracellular matrix, but it backfired, leading to a severe allergic reaction. “Immediately following the injections, my face began to blow up,” Johnson shared on social media.

The reaction occurred just before an interview with Bloomberg’s Ashlee Vance, prompting Johnson to warn the journalist, “You may not recognize me today. I hope I’m ok. If I’m not ok, are you by chance trained to perform any life-saving actions?” Fortunately, the swelling subsided after seven tense days, and Johnson’s face returned to normal.

The incident underscores the risks of Johnson’s aggressive approach to anti-aging. Earlier this year, he underwent a $20,000 gene therapy procedure aimed at extending his lifespan. The treatment, performed off the coast of Honduras, targets the follistatin gene, which may help improve muscle strength and slow aging.

Despite his dedication to radical anti-aging methods, Johnson has previously expressed concerns about the potential risks of DNA-altering treatments, particularly the possibility of triggering cancer. “If a therapy caused cancer in my body, there’d be nothing I could do to reverse the process,” he noted in a YouTube video.

Johnson’s experience serves as a stark reminder of the unpredictable consequences that can accompany cutting-edge biohacking practices, even as he continues his quest to defy the natural aging process.