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June 16th: The hygiene hypothesis misnomer and its potential impact on strategies to tackle antibiotic resistance

In the latest APUA newsletter-Liz Scott and Sally Bloomfield look at how ongoing obsession with the so-called hygiene hypothesis is undermining confidence in hygiene and affecting strategies to tackle antibiotic resistance.  Hygiene has a key part to play in tackling resistance by reducing the numbers of people seeking antibiotic treatment.

The evidence now shows that hygiene, as the public understands it, is not the underlying cause of the rise in allergic and other inflammatory diseases.  The evidence now indicates that the problem is most probably the combined result of lifestyle, medical and public health changes which, particularly in early life, deprive us of exposure to microbial “Old Friends”. These “Old Friends” microbes are not pathogens (as argued by the hygiene hypothesis) but the largely non-harmful species which inhabit the human gut and our natural environment. Changes which have been implicated in depriving us of exposure to OF microbes include sanitation, clean water and food, C-section rather than vaginal childbirth, bottle rather than breast feeding, fewer siblings, urbanisation and less outdoor activity.  Since communication between “Old Friends” and the immune system is mediated by the human microbiome, excessive antibiotic use and altered diet can affect the microbiome and further increase inflammatory disease risks.  The idea that “home and personal cleanliness” are the culprits is not supported by the evidence. 

The question then is how to connect with our microbial world, whilst at the same time protecting against infectious diseases. One thing is clear - we need a smarter approach to hygiene.  We need to understand that hygiene is more than “keeping ourselves and our living environment clean”. It is based on understanding the key routes of infection transmission, and targeting hygiene practices in the places and at the times that matter to break the “chain of infection”, particularly times associated with food, respiratory, hand and toilet hygiene, and homecare nursing etc.
The article concludes that attitudes to hygiene will not change until we dispel public misconceptions about the hygiene hypothesis, hygiene, cleanliness and germs. There is no doubt that we are going to have to view our microbial world very differently and abandon our germophobic ideas of living quite separately from our microbial world, which have persisted since the acceptance of the germ theory of disease in the late 19th century. But at the same time, we will need to redouble our efforts to regain confidence in hygiene and change hygiene behaviour to reduce the burden of infectious disease and protect antibiotic resources