The French fashion house creative director, 36, had bandages covering his entire upper body and head as well as burn marks on his face in a photo he posted on Saturday.
"A YEAR AGO," he began his lengthy caption. "I finally feel ready to share this. I've been hiding this for too long and it's time for you to know."
Rousteing explained, "Exactly a year ago, the fireplace inside my house exploded."
"I woke up the next morning in Paris' Hôpital Saint Louis. The talented staff at that famous hospital, which was dealing with an incredible number of COVID cases at that same time, took amazing care of me. I cannot thank them enough," he said of his treatment, later adding, "to the doctors and nurses at Saint Louis, and to all those who helped me during this long recovery and kept my secret: a profound thank-you. I love you."
The luxury fashion designer revealed he "did everything to hide this story from as many people as possible and trying to keep the secret with my teams and friends for too long ."
"To be honest I am not really sure why I was so ashamed, maybe this obsession with perfection that fashion is known for and my own insecurities…" Rousteing reflected. "And I truly realized that the power social media is to reveal only what you want to show! Kind of allowing us to create our own special narrative that avoids what we do not wish to see or show: this is our new world."
The Balmain designer shared that he dove straight into work during recovery in order to "forget" the reality of his health scare.
He inadvertently ended up wearing "face masks, turtlenecks, long sleeves and even multiple rings on all my fingers" when he had to attend anything for his clients.
"Now, a year later—healed, happy and healthy," the designer shared, adding, "I realize how truly blessed I am and I thank GOD everyday of my life."
Referring to the Balmain Spring/Summer 2022 fashion show on Sept. 29, Rousteing said it was "about the celebration of healing over pain and I thank all the models the productions my team the models my Balmain family, my friends that came and supported not only my 10 years of Balmain but my rebirth."
"Today, I feel so free, so good and so lucky. I'm beginning a new chapter with a smile on my face and a heart full of gratitude," the designer said. "GOD BLESS YOU ALL ♥️."
On his Instagram Story, Rousteing shared photos and videos of himself "hiding" while covered in long sleeve clothing and face masks during warmer months calling it the "most difficult summer of my life."
"Fashion can help to hide," he wrote over a photo of himself as Sia's "Unstoppable" played in the background. "And today I feel free. And thank [you] to all the people that helped me, supported me and loved me."
Rousteing's comments section was flooded with messages of support from his celebrity clientele.
Kim Kardashian commented, "🙏🏼 I love you." Cardi B wrote, "God bless you 🙏🏽." "Sending so much love & blessings," La La Anthony said. Lily Aldridge told the designer, "Sending so much love and thank you for sharing your story." "Thankfully you are ok! What a scary moment," Adriana Lima added. Tyson Beckford wrote, "Bless up you're still here and thriving my brother."
Rousteing, who at age 24 became the youngest and only Black creative director in the history of Balmain, has slowly been lowering the veil of his personal life.
Pascal Le Segretain/Getty
In the Netflix documentary Wonder Boy (which premiered exclusively in France last year), the designer didn't hold back as he allowed viewers to follow him on a search to find his biological parents while also opening up about experiencing racism in France, being lonely, and more.
"Many people know me as the Balmain designer, but I want to let them know the human being behind the French fashion house," Rousteing told PEOPLE in June, admitting that he was "nervous" to show that side of him.
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Out of all the things fans might be surprised to see in the film, the fashion figure candidly shared that "the loneliness" is probably an aspect of life that is unexpected.
"They see me with my friends and celebrities and [living] this incredible, glamorous life. Everything looks fabulous. But this documentary shows the loneliness of someone who's looking for his parents and trying to understand his origins. I think people will be surprised to see me being vulnerable and fragile."
Stefanie Keenan/Getty Images for BALMAIN
Among other things, the designer shared his commitment to diversifying the fashion industry.
"I was kind of bored with fashion sometimes being so unreal and disconnected from reality. Even the bodies of the models. People look through fashion magazines and think, 'Who actually looks like that?'" Rousteing told PEOPLE. "The celebrities I work with bring an awareness of Balmain to a different [demographic] that doesn't open a magazine or follow fashion."
When asked about his career-defining moments, the star cites tapping Rihanna as the face of Balmain in 2013, launching an affordable collection in collaboration with H&M in 2015, and designing Coachella looks for the one and only Queen Bey in 2018.
"Just being next to Beyoncé, listening to her voice, cutting the fabric together on the floor... I felt like someone should have pinched me," he said, adding, "it was surreal."
Additionally, Rousteing gushed about having support from the Kardashian-Jenners, telling PEOPLE, "Kris Jenner is like a mom to me. Whatever I go through in my life, I know I can count on her. She's always there for me."