Charlize Theron is so nervous about making public speeches, she often relies on alcohol to loosen her up before she steps out.

The Oscar-winning actress, who blames a combination of liquor and painkilling medication on her decision to kiss Shirley Maclaine's buttocks at a recent event, admits that she's extremely shy when about speaking to large groups of people.

She says, "I'm horrible with public (speaking). (Alcohol) helps.

"Acting is actually quite intimate. It's a very intimate process and it's a smaller environment and it's not like theatre or anything like that.

"I get blackness and white spots and then I break out in hives (before making a speech). And I'm just always so scared I'm gonna offend somebody or forget to mention somebody.

"I'm a horrible public speaker, so I'm always nervous."