What is the hygiene hypothesis?

#MSBlog: How clean was your childhood? Did you neglect to educate your immune system and now have MS?

Rook GA. Hygiene hypothesis and autoimmune diseases. Clin Rev Allergy Immunol. 2012 Feb;42(1):5-15. doi: 10.1007/s12016-011-8285-8.

Throughout the twentieth century, there were striking increases in the incidences of many chronic inflammatory disorders in the rich developed countries. These included autoimmune disorders such as Type 1 diabetes and MS. Although genetics and specific triggering mechanisms such as molecular mimicry and viruses are likely to be involved, the increases have been so rapid that any explanation that omits environmental change is incomplete. This chapter suggests that a series of environmental factors, most of them microbial, have led to a decrease in the efficiency of our immunoregulatory mechanisms because we are in a state of evolved dependence on organisms with which we co-evolved (and that had to be tolerated) as inducers of immunoregulatory circuits. These organisms (“Old Friends”) are depleted from the modern urban environment. Rather than considering fetal programming by maternal microbial exposures, neonatal programming, the hygiene hypothesis, gut microbiota, and diet as separate and competing hypotheses, he attempts to integrate these ideas under a single umbrella concept that can provide the missing immunoregulatory environmental factor that is needed to explain the recent increases in autoimmune disease.

“These graphs demonstrate that as the incidence of infections has plummeted the incidence of common autoimmune diseases has soared. It does make you question what we are doing to ourselves and why.”

“Our modern sterile, or clean, environment without parasitic and other infections have left our immune systems immature and uneducated. The lack of infections have left our immune systems prone to develop autoimmunity. This is one of the reasons why the incidence of MS is increasing so rapidly and underpins the science of using parasitic infections as a treatement for MS and other autoimmune diseases.” 

11 thoughts on “What is the hygiene hypothesis?”

  1. Very true – how was my early childhood? Sterile almost with no siblings and little outside contact meaning that I got all the children's viruses late in life. So how would the parasitic treatment look like?

  2. Studies has been done earlier with very positive resultshttp://www.ncbi.nlm.nih.gov/pubmed/17230481http://www.ncbi.nlm.nih.gov/pubmed/21277637

  3. I did not have a particularly 'sterile' childhood, spent a lot of time at the stables and generally outside, certainly nothing like the overkill you hear of theses days. However, even my experience was probably fairly sterile compared with previous generations, and ailments were treated with antibiotics. I suppose it depends how clean is clean/sterile?

  4. This is a nice example of the causation / correlation problem. 😀 For me I would say that I had a more "dirty" childhood and still catched MS.It may be true, that ppl today are less infected with parasitic crawlers but we have a lot of other stuff which ppl 100 years ago didn't have.And don't forget the "telescope effect". > 100 years ago ppl didn't visit a dacotor that often as today becase it was unaffordable. I think the spanish flu had a big impact on that behaviour and changed also the policy of doctors or the state insurance systems.So I wont trust the "more diseases theory" overall.Do we have more stars than 100 years ago?No!We have better telescopes!

  5. I had a very mucky childhood, mainly left to my own devices to grub around in the soil. I contracted all childhood diseases including measles, mumps, whooping cough and scarlet fever. I remember having hook worms, it probably wasn't an isolated incident. I now have MS and my sister has a different auto-immune disease. I don't buy the hygiene theory and I would suggest diet as a more obvious link with the development of MS.

  6. You know, I was a child in the '80s and a teenager in the '90s. I believe that I was the last generation to have a 'proper' childhood, the kind where we were expected to go out and play until dinner time, and then go play some more afterwards. It may just have been fooling about on the suburban streets we grew up in, but it was still outdoorsy. Alas, I too got MS but perhaps my sanatised middle-class environment was too clean for essential viruses and bacteria. Maybe our food lacked grit. Who knows.One thing for sure, if this theory is correct then the kids born after the millennium change will fare even worse. It's a time bomb waiting to explode. Ka-boom!

  7. As well as an upbringing where I was not overly protected as a boy, suffered all the usual childhood ailments, winter born, loads and loads of sunshine (12 weeks a year in Mediterranean), healthy home cooked food, only occurrence of MS in the family was father's sister. I had first relapse in 79, diagnosed in 95 and SPMS by 2000. Sometimes the toast has jam & butter on both sides when it falls onto the floor. Could be caused by EBV, diet, environment, genetics or a mixture of the four.Patrick

  8. I spent my childhood in Africa, playing dirt and crowds of children on the streets. In my adult life I was diagnosed with Ulcerative Colitis. How does the Hygiene theory fit into this?

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