Out Damned Spot! Out I Say!

So saith the conscience-stricken Lady Macbeth in Act V Scene I of Shakespeare's Scottish play as she is watched by her waiting woman and a doctor. They have found her sleepwalking about the castle, absorbed in her desperate attempts to wash away the blood of the murdered Banquo from her hands.
Obviously, no-one told Lady Macbeth about the U of T study just published in the journal "Science" under the article title "Washing Away Your Sins:Threatened Morality and Physical Cleansing". Conducted by Katie A. Liljenquist and Chen-Bo Zhong, the study consisted of a series of four experiments that involved students at Chicago's Northwestern University. The findings showed that "physical cleansing alleviated the upsetting consequences of unethical behaviour and reduced threats to one's moral self image". The article's authors noted that "ethically compromised individuals experienced an increased desire to cleanse themselves" and dubbed the observed psychological benefits of a good scrub-down the "Macbeth effect".
Lady Macbeth bemoans the fact that "Here's the smell of the blood still. All the perfumes of Arabia will not sweeten this little hand". If only she had been able to talk to G.W. Bush. He could have told her, all she needed was a good ol'-fashioned bar of soap.
I bet he goes through a dozen a day.