Ben Goldacre
Thursday July 8, 2004
The Guardian

· In the battle against pseudoscience, the Advertising Standards Authority is another cheerfully toothless body. But there is room, at least, for one man to worry a big corporation with a humiliatingly public rap on the knuckles. Teacher and Bad Science reader David Andrews complained to the ASA about the preposterous claim Cussons made about its Carex soap: that it can tell the difference between “good” and “bad” bacteria. Whatever they’re supposed to be. The ad features two kittens. One has big teeth and evil eyes, and is labelled “bad bacteria”. The other is “good bacteria”. Can you expand on that, Cussons? “Look at your hands. You can’t see the good and bad bacteria, let alone tell them apart. But, thankfully, Carex can. Its unique formulation cares for the good bacteria, whilst being strong enough to fight the bad.” But how? “Carex knows the difference.”

· Now this is an interesting idea. There are all kinds of bacteria out there, doing all kinds of things, in the soil, in your poo, up your nose, in volcanos, and anywhere you can think of. Whether they’re good or bad for you depends on things like what they eat, or what they make. Some of them eat up things that are bad for you. Some of them make things you need. Some of them, quite accidentally, make things that happen to bind to little receptors in your gut, switch on the goo production machine, and leave you clinging to the toilet bowl. These are “virulence factors”. The idea that chemicals in a soap can work out what all these bugs are up to, and then predict how they will interact with the human body, is fantastic. If, like me, you have ever taken an antibiotic called Augmentin to kill off a “bad bacteria” infection, for example, you will probably have experienced the green sludge that comes out of your bum as a result of the “good bacteria” being accidentally killed off at the same time. Molecules clearly have a bit of difficulty making this important distinction.

· But Cussons fought back. Of course soap kills bacteria in general. It asserted that “although the figure was not statistically significant, almost twice as many good bacteria remained on hands after washing with Carex, compared with washing with plain water … although many good bacteria were removed during washing with Carex, that removal was caused by mechanical action”. The advert was deemed misleading, and has been banned. But, of course, the bottles contain the same ridiculous claim. Trading Standards anyone?