According to the unqualified quacks flogging the idea at £60 a pop, it can help you lose weight, flush out toxins, boost your immune system and make you feel good.
Trouble is, the whole idea is bullshit.
New research from the University of the Bleeding Obvious shows that introducing a pressure washer to your bum isn't terribly good for you.
It transpires that sending water the wrong way round a one-way system can make you bloated. Gosh.
It also makes you vomit (never!), gives you cramps (no!), washes loads of good stuff out of your body (really?) and will completely nalls up your kidneys. It can even burst your bowel.
Colonic irrigation was first practiced by the ancient Egyptians, who while being quite clever in terms of architecture, astronomy and funky eyeliner were pretty rubbish on the more important stuff like bacteria, working conditions of manual labourers and not marrying your own sister. I wouldn't take their advice on bubble bath, much less anything to do with my insides.
That's because sticking a pipe up your bum is also pointless.
There are no such things as 'toxins' up there. Anything is a toxin, if you eat enough of it. A lawn can be toxic, ham sandwiches, Christmas cake. Nasty, evil poisons trying to kill you simply don't exist - just things that might do you harm, if there's too much of them and you're a bit unlucky or an idiot.
If you're genuinely poisoned, the body generally notices and empties itself fairly quickly from one end or the other. The ingredients of a modern diet - red meat, white bread, caffeine, alcohol - do not stay in your body or gunk anything up. Your liver and kidneys and perspiration and colon do an astounding job cleaning all that stuff out, 24 hours a day, seven days a week. They do it whether you've eaten junk food or organic dolphin-friendly lettuce or drunk a load of Guinness, and people who have regular colonics actually find their natural processes slow down or stop altogether.
If you want your organs to process your food better you need to take some exercise, get plenty of sleep, and not do any one thing to excess.
And if you want to lose weight, get rid of the nasty stuff and feel good, there is a guaranteed and above-all cheap way of doing it.
It's called HAVING A POO.
Don't make me tell you again.