• Question: what is the good dirt hypothesis?

    Asked by yerseenee to MarkF, Mark, Michael, Panos, Sarah on 21 Jun 2010 in Categories: .
    • Photo: Sarah Burl

      Sarah Burl answered on 15 Jun 2010:

      this is sometimes referred to as the ‘Hygiene Hypothesis’ which is based on the idea that is you are exposed to dirt at a young age then you will develop good immunity to many things which will help protect you from diseases and from getting allergy. If you are too sterile then you are more likely to get allergy. This is supposed to explain why there is more allergy in the Western World then in the developing world. There is a lot of talk about this theory and some people don’t believe it. Without talking about too much immunology there are several arms of immunology, one produces good ‘pro-inflammatory’ responses and another produces ‘anti-inflammatory’ responses. Allergy and is anti-inflammatory and response to dirt is pro-inflammatory. the balance of these responses is very important for keeping us healthy.

    • Photo: Mark Travis

      Mark Travis answered on 15 Jun 2010:

      What I think you are referring to is the idea that if we get a bit dirty, it is actually good for us?

      There is an idea that is very popular with a lot of scientists called the ‘hygiene hypothesis’. It is used to explain the fact that in most countries in the Western world, in recent years there has been a massive increase in the number of people who have allergies in inner cities whereas this isn’t seen in people who live in more rural areas (i.e. on farms). Some scientists claim that this is due to us being too clean now-a-days; children in inner cities today don’t see as many bacteria and other microbes as kids in older days, as people are more careful about sterilising everything and keeping everything super clean. So, when the immune system sees an allergen like pollen or nuts, it goes crazy and causes an allergic reaction. Whereas people in less developed countries (and those on farms) don’t live in such a clean environment (so they say), so their immune systems are tickled all through childhood. So, when they see something that can cause an allergy, they ignore it.

      Bit complicated I know, but basically there are a lot of people who think we are too clean now-a-days…… but we have to be careful because if we aren’t clean enough we can get ill as well!! I think there is some truth to us being too clean, but wouldn’t recommend letting babies roll about in the mud…..

    • Photo: Mark Fogg

      Mark Fogg answered on 15 Jun 2010:

      It’s a long answer, but it’s an important question that deserves it, hope you don’t mind 😉

      The ‘good’ dirt or ‘Hygiene hypothesis’
      Your immune system needs to ‘learn’ how to work properly. It learns by coming into contact with many different types of bugs, like those found naturally in the environment. Then in the future, when it sees a bug, it recognises it easily and gets rid. However, if your immune system hasn’t been properly trained, because you’ve been too clean, it over reacts to things it finds in your body. Sure, it recognises bugs, but it also sees stuff that can’t do any harm, like dust and pollen, as something nasty. That’s where the allergies come from, your immune system is reacting to harmless things as well as nasties.

      I think of it as the ‘cat and thistle’ hypothesis

      You learn early in life the difference between a harmless cat and a thistle. Because you learned this difference at an early age, when you see a cat and a thistle in a garden full of flowers, you get rid of the thistle and leave your cat alone; you know it’s harmless. If you were very stupid and hadn’t learned the difference, you could throw your cat away as well as the thistle, because you see both as something that shouldn’t be in a flower garden.

    • Photo: Panos Soultanas

      Panos Soultanas answered on 16 Jun 2010:

      Hi yerseenee,

      Google (great tool…) has come up with a good site to get moe information on this;

      http://news.bbc.co.uk/1/hi/health/8373690.stm

      have a look.

    • Photo: Michael Loughlin

      Michael Loughlin answered on 21 Jun 2010:

      the theory that an early immune system requires to “see” bacteria in order to prepare and train up to be an active working immune system

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