This young Asian guy decides he wants to enter a marathon. He's quite fit, trains well for a long while and finally the day for the marathon arrived.
All went well until he came to the finish but then he found he just couldn't stop ... had to keep running though he didn't want to. So he though the best thing he could do was to run home. Even there he couldn't stop running round the house and by now he was beginning to tire... but his legs wouldn't stop moving.
He managed to get to the doctor's ... the doctor looked at him, asked if he'd trained properly etc etc, but couldn't understand what was wrong, so he sent him to the hospital accidents and emergencies wing. They too were puzzled, the poor guy was beginning to look totally exhausted ... but his legs wouldn't stop.
Finally they called one certain specialist and asked if the guy could be seen straight away. So in he went, still running, till the specialist examined him, and then gave him a small box containing a white powder, with a glass of water.
"Empty this box into the water," said the doctor, "then drink it."
This done, the Asian guy suddenly stopped running! A marvelous cure!
Exhausted, the guy beamed ear to ear.
"What was that?" he asked.
"Persil," said the doctor. "It's well known to stop coloureds running."