Kelly Osbourne "lost it" and got drunk on a plane after researching her brother Jack's multiple sclerosis.
The Fashion Police presenter turned to alcohol on a flight from Los Angeles to Atlanta on 19 June after studying websites about the illness made her upset.
Kelly - who has been in rehab twice before - told RadarOnline.com: "I got drunk on the plane to Atlanta.
"It was on an empty stomach, and before I got on the plane a gentleman came up to me and asked me how my brother was doing and told me about his brother having MS and directed me towards a website.
"On the plane I started looking at the website. It described how bad certain cases of MS got, and it made me lose it because I've sat through my mother having cancer, my dad almost dying from a bike accident, and now it's my brother who's my best friend. I lost it."
However, Kelly says doesn't want her brother's medical condition to be her excuse for getting drunk.
She said: "I can't stand knowing that he probably is thinking that it was because of him being diagnosed that I made a fool of myself. I made a fool of myself regardless of Jack and I hate that that's even out there.
"I hate the fact that I'm sitting here right now, and that's even an excuse because it's not an excuse."
Despite previously spending time in rehab, Kelly does enjoy the occasional drink.
She said: "I have not lied about it. I have the occasional drink. I will never lie about that. That's my choice that I make and I'm an adult and I have to be responsible for my actions.
"But it's not like I was so out of it they had to land the plane or something. I got drunk on a plane, big deal.
"The way I live my life after going to rehab is not the way that most people do. It isn't. Yes, I still drink and I've always said that. I do have the occasional drink. I'm not using [drugs], I haven't. I won't. I'm not going to do that."
A fellow passenger had claimed Kelly was crying and had to be helped off the plane when it landed.