Have you ever wondered how Demi Moore manages to look ageless? The actress revealed her secret during her appearance on last night's episode of the Late Show with David Letterman.

Aside from the usual cosmetics, beauty treatments and plastic surgery that help Hollywood stars enhance and maintain their health and good looks, some celebrities would do just about anything to keep looking young.

Admitting she is constantly searching for "the cutting edge in health and healing," Demi Moore revealed on Letterman's show that she recently underwent a cleansing treatment in Austria, which included leech therapy.

"A month ago I was in Austria doing a cleanse. And one treatment was leech therapy," she said, "These aren't swamp leeches; they were highly trained medical leeches. High level bloodsuckers. It detoxifies your blood. And they have a little enzyme that when they are biting down on you is released in your blood."

She explained the technique saying she had to take a turpentine bath before allowing herself to be covered in leeches. They initially tested a leech out on her belly button before placing several others on different areas of her body. She also revealed that the creatures prefer bare skin.

"Leeches don’t like hair, they much prefer a Brazilian," she said.

"It crawls into your belly button and it bites down and then you relax and you watch it swell up and get fatter and fatter. And when it's super drunk on your blood, it just rolls over like its drunk in a bar. You first feel worse and then you feel better. I'm feeling very detoxified," the 45-year-old actress said, adding that she would be interested in repeating the treatment again.

In medieval times, leeches were used to remove blood from a patient to balance the "humors". The four humors of ancient medical theory were blood, phlegm, black bile and yellow bile.

Leech therapy always used to be used to relieve pain and inflammation, but fell out of favor last century. Today there is a real clinical application in that they are of great value to plastic surgeons when venous congestion of skin and muscle flaps is a problem.

Medical use of leeches also includes treatment of black eyes, and hirudin is used in the treatment of inflammation of the middle ear. Hirudin is also being developed for experimental use as a systemic anticoagulant, and may prove useful in invitro blood sampling.