Stuff that occurs to me

All of my 'how to' posts are tagged here. The most popular posts are about blocking and private accounts on Twitter, also the science communication jobs list. None of the science or medical information I might post to this blog should be taken as medical advice (I'm not medically trained).

Think of this blog as a sort of nursery for my half-baked ideas hence 'stuff that occurs to me'.

Contact: @JoBrodie Email: jo DOT brodie AT gmx DOT com

Science in London: The 2016 scientific society talks in London blog post

Sunday, 27 June 2010

Dettol kills extremophiles. Fact. (Maybe)

Here we go. Another blog post to put down some thoughts before complaining to the Advertising Standards Authority about a strange claim made by Dettol in a recent advert.

I didn't get the exact phrasing but it seemed to be along the lines of bacteria can survive in lava so some of them are a bit indestructible but fear not, for Dettol can get rid of them on your kitchen surface.

I have some questions that I want to investigate, before having a formal whinge, which are...

1. Can bacteria survive in lava?
Lava's pretty hot (quite a bit hotter than those hydrothermal vents I think?) so I wouldn't be surprised if they'd struggle to survive in the sort of lava that's pumping out of an active volcano. Equally, bacteria have turned out to be fairly flexible in the range of environments they can surve in and Wikipedia has a long list of the various 'extremophiles' (, so maybe they can.

Of course, lava's only hot for a short time. It soon cools (and as an interesting aside the rate at which it cools determines the type of volcanic rock it produces). Cool lava can presumably contain the sort of bacteria that like to live inside rocks; apparently these are called endolithic bacteria. I don't know though if the bacteria move in at a particular temperature, or if they manage fine at any temperature of lava, even at its hottest.

2. How common are these bacteria? Do they live on my kitchen surface?
I'm assuming the sorts of bacteria that like living in volcanic rock aren't the same ones that I'll find in my kitchen. It doesn't particularly matter if Dettol can kill these bacteria if the bacteria are nowhere to be found in my flat. Question 2b is 'can Dettol kill lava-dwelling endoliths?' which is not a question I expected to be asking myself when I woke up this morning.

3. Is it appropriate for Dettol to draw these inferences from 'badass' bacteria? (See Youtube comments)
@medtek and @jdc325 have kindly sent me a link to the original advert so I can check the exact phrasing and amend this blog post later (those dishes won't wash themselves...)

Dettol Complete Clean Advert

Clearly they are implying that some bacteria are 'tough' and require firm handling, but I thought the tone of the ad was a bit overkill. Question 3b is 'how effective is soap and water at getting rid of surface bacteria?'


  1. The thing that gets me with these adverts is that they talk about killing 99% of all germs. In order to do that, they need to know exactly how many there are. Which I doubt. And even if they did, what is that 1% that they can't kill? Is it the same 1% the others all have as well?

  2. If the one per cent are the really nasty bacteria then killing all the less awful ones mightn't be so great. I expect the one per cent that remain will quickly regroup and take over my kitchen, without the inhibiting effect of the others. Then where will I be ;-)

  3. Well Jo lets see if I can answer some of your questions as the Hon General Secretary of the Society for Applied Microbiology....
    1. Hmm bacteria survive 1000 degrees centigrade, very unlikely. Some evidence of bacterial life has been seen in rock and lava flows but this is more likely organisms and material trapped inside a large block of rock that was carried along in a lava flow. 2. How common are these bacteria? Well I am assuming that you are referring to the strains that are geologically associated, well not that common and most of these types of organisms are environment specific, so it is extremely unlikely that the same organism will appear in your kitchen, unless of course you are cooking on the rim of a volcano!!
    3. I think when trying to demonstrate that you have an effective product in whatever realm you need to use realistic comparators. I personally do not feel that that this has happened here. It would have been far better to tell us what it does actually kill and that it does kill the organisms that are more likely to be found in a Kitchen rather to have gone for dramatic effect.
    Dr Mark Fielder (Hon Gen Sec. Soc Applied Microbiology)


Comment policy: I enthusiastically welcome corrections and I entertain polite disagreement ;) Because of the nature of this blog it attracts a LOT - 5 a day at the moment - of spam comments (I write about spam practices,misleading marketing and unevidenced quackery) and so I'm more likely to post a pasted version of your comment, removing any hyperlinks.

Comments written in ALL CAPS LOCK will be deleted and I won't publish any pro-homeopathy comments, that ship has sailed I'm afraid (it's nonsense).