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Medical Why Doesn't Diatomaceous Earth Cut Humans?

  1. Jun 24, 2012 #1
    Diatomaceous earth is a very fine white powder, used for insect control among other things. According to my research on the webernets, it works by "cutting up" the exoskeletons of insects, and drying them out resulting in death.

    Because this substance works through mechanical means rather than chemical, it is completely harmless to humans, pets (except your Madagascar cockroach), and is even found in many foods that we eat.

    However, no amount of searching I do can find me an answer to the simple question: why doesn't it cut humans? The only answer that I get is that it is "too small." Huh? If I have a sharp knife, and I make it even smaller, it's only become sharper, thus more capable of cutting me. How is this substance able to cut insects but not humans?
  2. jcsd
  3. Jun 24, 2012 #2
    I looked into this a few months back and what I read is not that it "cuts" insects per se, but that it gets stuck in their joints and the more they move the more it gets driven into the soft tissue there. It's the right size and sharpness for that. Human skin cells don't grind against each other in a way that would drive the DE deeper in between them.

    I'm not completely sure why it's safe for internal use but I would deduce it's because, the alimentary tract between the mouth and stomach is protected by mucous, and, once in the stomach the DE, which is calcium carbonate, is quickly dissolved by stomach acids.
  4. Jun 24, 2012 #3
    Yeah, I've considered the possibility that "cut" isn't necessarily used in a literal sense as we imagine it. That could be the explanation.
  5. Jun 24, 2012 #4


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    I understood (though I may be wrong) that where it does its damage is in the breathing canals in an insect's abdomen. If the diatomaceous earth is just the right size, it will get jammed in there and wreak havoc.

    If our alveoli have a different dimension - larger or smaller - then no jamming.
  6. Jun 24, 2012 #5
    This would certainly kill them faster than immobilization.
  7. Jun 24, 2012 #6
    While this sounds plausible, I'm pretty sure that it has nothing to do with inhalation, according to the sources I've looked at.
  8. Jun 24, 2012 #7


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  9. Jun 25, 2012 #8


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    More information here, method of action starts on page 339:
    http://www.ksre.ksu.edu/grsc_subi/Teaching/GRSC651/GRSC651_Courses_Material/lecture_slides/GRSC651_lect_20(1)_Inert_Dusts.pdf [Broken]

    Be careful with inhalation if the dust is based on silica crystals.
    Last edited by a moderator: May 6, 2017
  10. Jun 25, 2012 #9
    Interesting! It soaks up their wax covering and they dry out.

    And not calcium carbonate as I thought, though there's no safe dust to inhale.
    Last edited by a moderator: May 6, 2017
  11. Jul 20, 2012 #10
    Bumping this as I never got a totally clear answer.
  12. Jul 20, 2012 #11


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    Can you explain what is not clear to you?
  13. Jul 20, 2012 #12
    Go to p. 340 of Monique's link and read "Proposed Modes of Action". This is the best info anyone has dug up.

    Their best bet is that DE absorbs the wax ( epicuticular lipid layers) from the insect's outer shell. That wax is holding their moisture in, so without it they dry up and that leads to their death. There are pictures of a bug there covered with dust that has soaked up it's wax: looks covered in white moss.
  14. Jul 20, 2012 #13
    So it doesn't have anything to do with cutting or chipping away the exoskeleton, but simply dries them out?

    That sounds like an acceptable answer, but if that's the case then it's odd that most sources describe DE to "cut" insects.

    I haven't seen a satisfactory answer to the question in the title. Unless the DE doesn't cut insects in the first place, in which case it's just misleading.
    Last edited: Jul 20, 2012
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