Sacha Baron Cohen was struck down with an embarrassing ailment while filming his new movie Bruno - he reportedly suffered an allergic reaction while bleaching his body hair.

The British funnyman decided he needed have smooth skin to play the outrageous gay fashion journalist - but instead of opting for a painful waxing treatment, the comic decided to lighten his body hair instead.

But Cohen's plan backfired when a burning rash broke out all over his body in reaction to the bleach, according to British newspaper The Sun.

A source tells the publication, "Sacha is committed to as much realism as he can muster in his films. He'd heard all-over hairlessness is a popular trend in the gay community, so he thought he would bleach all his hair so it would look invisible. But it turned into a disaster.

"He had a bad allergic reaction to the hydrogen peroxide. It was so severe he couldn't sit down for three days. He had to make an emergency appointment with a doctor, who gave him medication to counter the irritation."