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Anna Crist

student researcher , University of Oregon

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Purell now, Bacteri-ell later?

The hygiene hypothesis, the idea that “too much cleanliness prevents the development of a well-balanced immune response”(Sironi and Clerici, 2010), has received a lot of support and also criticism. It has recently been challenged by the hypothesis of “early immune challenge”, which states that a lack of appropriate immune stimulation during early childhood might account for the increased development of allergies in industrialized countries (Kramer et al, 2013). This proposal places less emphasis on excessive hygienic practices and focuses more on the insufficient exposure to specific environmental microbes, particularly those from non-urban environments, as the reason behind the rise of atopic disease. While different, both hypotheses point to the beneficial health affects of some microbes.

What do you think is the reason for increased allergy levels in industrialized countries? Do you think that a concoction of the “right” microbial species in the form of a lotion, drink, or inhalant (aka "Bacteri-ell") could be a future replacement for natural exposure to beneficial microbes?
Instead of using hand sanitizers like Purell, do you see a future where people from some regions of the world are unsanitizing their hands with “Bacteri-ell”?

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  • Apr 29 2013: According to the National Institute of Health it was found that from 1988-1994 more than 50% of Americans from ages 6-59 were sensitive to at least one allergen. However, a similar study done in 1980 found rates 2-5 times lower. The reason for this large increase in allergens is thought to be the more sterile lifestyles we now live. By disinfecting everything around us, we are severely limiting the amount of bacteria we are exposed to.

    Being exposed to different bacteria at a young age is very similar to receiving a vaccination. A vaccination works by stimulating an individual's immune system in order to develop an immunity to a pathogen. Our bodies immune systems are formed by being exposed to seemingly harmless substances around us, such as pollen, animals, foods, etc. When we do not receive these "vaccinations" of harmless substances at a young age, it can result in allergies later in life when they are finally encountered.
    Exposure to certain germs and allergens at a young age are important in the development of our immune systems. Without these exposures our bodies will be unable to fight off everyday substances later in life.
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      Apr 30 2013: Julia,
      That is a fantastic summary of the hygiene hypothesis and why it really seems like it is addressing the newer early immune hypothesis with its premise. It got me to thinking though, since so much of both hypotheses are based on early exposure and the conditioning of our immune systems for the rest of our lives, I have to wonder if there is any hope to the strategy of introducing the missing agents later in life in order to cure allergies or other auto immune diseases. I bet that if the supplementation of microbes, like with the "Bacteri-ell" discussed by Anna, was done early enough while the immune system was still plastic, it would be possible to avoid the development of autoimmune diseases including allergies. If this window of developmental plasticity is missed though, I don't think that this sort of treatment would be effective.
      I would love to know if there is any evidence that autoimmune diseases can be treated in this way later in life though, it isn't something I really follow so it wouldn't surprise me if there were some new developments since last I heard about the general theory.
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        Apr 30 2013: Thanks for your input! In my head I imagined parents lathering up their children with Bacteria-ell lotion, instead of trying to keep them germ-free with sanitizing agents like Purell.

        Support for the “hypothesis of early immune challenge” comes from a study by Douwes, et al (2008) which found that children raised on farms were not afflicted with asthma and neurodermitis as much as children who were raised in cities. This observation was even associated with contact of pregnant women to animals and soil, suggesting that prenatal exposure to certain microbes is also important in disease prevention. I thought this was really interesting!

        I am out of time right now so I will get back to you about adult studies I found! Or maybe someone else can contribute to that part of your comment.
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          Apr 30 2013: I guess the main thing that had me confused about the early immune challenge was how it was really differentiated from the older hygiene hypothesis. You said in the intro that "[The early immune challenge hypothesis] places less emphasis on excessive hygienic practices and focuses more on the insufficient exposure to specific environmental microbes," but wouldn't this lower exposure to microbes be a direct effect of the hygiene hypothesis. I guess it seems like the main differentiation between the two is where the microbes are coming from then, be it urban or rural areas, but I still feel like I'm missing some larger point of distinction between the two.
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        Apr 30 2013: I was also confused about the difference between the two at first. This quote, which I also mentioned to someone else, will hopefully help clear things up a little.

        "The risk of developing allergies is not necessarily caused by a lack of bugs and parasites in the environment per se, but rather by a lack of certain organisms that have, over the course of evolution, trained our immune system to be more tolerant.” (Rook et al, 2009)

        The first part (up until "per se") describes the hygiene hypothesis, or the idea that not being exposed to enough microbes *in general*, due to more sanitation, causes us to be more prone to certain diseases. Whereas the second part of the quote is more along the lines of the "early immune challege" hypothesis, the idea that lack of exposure to SPECIFIC bacteria is the cause of increased allergies. It's definitely a subtle difference, but I hope this helps!
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          Apr 30 2013: I was wondering that as well, and that clears it up for me at least. I think the early immune challenge hypothesis sounds more plausible, as i suspect that certain distinct specific microbes are what make the difference- however, it's possible that so many different specific microbes are needed that this nearly replicates the hygiene hypothesis. I suppose it depends on where one draws the line between "many many specific microbes" vs "a general diversity of microbes," however, with that said, i imagine more than a few denizens of our microbiome are innocuous or at least have no noticeable effect on human immune response.

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