Nadiya Hussain gets triggered by the toilet because of traumatic childhood bullying.
The "Great British Bake Off" star - who has suffered panic attacks and anxiety since the age of 10 due to her primary school experiences - has been told she suffers from post-traumatic stress disorder (PTSD) as a result of her head being flushed down the toilet and thinking she was going to drown.
Speaking candidly on ITV's "Loose Women", she said: "My sister lives in a flat, and as you go up her stairs the first thing you see is her bathroom door.
"To this day, when I go up I can't - every time I go to the toilet, I cannot take that image out of my head.
"I've tried for years to get away of that image but I can't. That was the first time I had a panic attack, when my head was flushed down a toilet."
The 34-year-old star has opened up about her mental health in new BBC documentary "Nadiya: Anxiety and Me", and she admitted she was shocked to discover she was suffering from PTSD because she associated the disorder with the likes of war veterans.
She added: "That was the biggest surprise for me, to hear that it was PTSD. For years I thought it was panic disorder and anxiety, so to hear PTSD was a massive shock for me.
"I hadn't realised what it was. When you hear PTSD, you hear people who went to war and fought for their country.
"My head was flushed down the toilet, but when you're 11 that's enough to make you really sick."
And although Nadiya is glad to have spoken out about her own experiences for the BBC programme, she conceded despite being honest in the past, it was still difficult exposing so much of herself to the nation.
She said: "I talk about it but just little bits. So, yes and no. It wasn't easy. Yes because I wanted to, because it's important to talk about it. And no, because what on earth, that's quite a lot of yourself to give up. It was tough."
"Nadiya: Anxiety and Me" airs tonight (15.05.19) on BBC One at 9pm.