I'm glad I'm not the only one with too much maths to take this seriously.

I saw this on xkcd the other day:

What’s always bothered me about this claim is that everyone knows bacteria grow exponentially. If you kill 99.99% of them, they need only double about 13.3 times before the population returs to its original size. Under optimal conditions, that’s roughly 133 minutes. That’s only as long as it takes to watch Donnie Darko or have a perfect Christmas. If you wash your hands, kitchen or whatever less often than that, the bacteria will win.

And I’m pretty sure Dettol only claims to kill 99.9% of germs. That might not sound like much, a difference of 0.09%, but it only takes bacteria 98 minutes to claw back that difference. That’s a quarter of an hour you’ve lost.

But I can see how their marketing people thought “kills 99.99% of all germs” sounded better than “buys you an hour and a half in your doomed battle against the unstoppable onslaught of disease”.