The hygiene hypothesis: are we too clean?

Now this might seem a strange article to follow the one entitled ‘The importance of good hygiene for good health’, but it is always crucial to strike a balance so that we don’t go too far in living in almost a sterile environment. 

The common belief that has driven medicine, as well as public perception and hygiene practices, is that when we get sick it’s because of something we ate, or inhaled, or were exposed to in other ways. The hygiene hypothesis, however, points in a different direction, proposing that in many diseases it is a lack of exposure to the “bad guys” that causes harm.


Increased hygiene and a lack of exposure to various micro-organisms may be affecting the immune systems of many populations – particularly in highly developed countries like the US and UK – to the degree that individuals are losing their bodily ability to fight off certain diseases. That’s the essence of the “hygiene hypothesis”, a fairly new school of thought that argues that rising incidence of asthma, inflammatory bowel disease, multiple sclerosis and perhaps several other autoimmune diseases may be, at least in part, the result of lifestyle and environmental changes that have made us too “clean” for our own good.


The hygiene hypothesis suggests that it is the more hygienic ones who are more susceptible to autoimmune diseases. The argument is – though we don’t yet have proof of it – that the immune system needs some kind of hardening, some kind of resistance in order to function optimally.


While the evidence is by no means clear-cut, some studies show that children who lived on farms when they were very young have a reduced incidence of asthma, which has led several researchers to conclude that organisms in cattle dust and manure may be the stimuli that their immune systems needed to fight off asthma. Other research found that ultra-clean children were more likely to suffer from eczema and/or wheezing than children with less hygienic habits. The more hygienic the child, the more likely he or she was to be affected.


Supporters of the hygiene hypothesis have not proposed that “playing in the dirt,” or making society less hygienic in general, are useful goals in medicine. But they do propose that to keep the immune system working properly, you need controlled stimulus or else it doesn’t know how to recognize the bad guys.


So, are we too clean? Research is definitely pointing to dirty kids being healthier kids, and growing up to be healthier adults. Dirt, it seems, isn’t always dirty, and bacteria isn’t always bad. Getting obsessive about cleanliness and sterilisation and keeping children ultra clean isn’t recommended, but this doesn’t mean hygiene isn’t important. Once again a balanced approach seems to be the answer. As long as you wash your hands at appropriate times and keep your living and working environment as clean you can but don’t get obsessive about it, you’ll be getting the balance about right. Life, after all, is for living, not for cleaning.

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