For most of us in the Industrialised world we have certain luxuries. Luxuries like a roof over our head to keep out the elements, and in particular those savage Winters we have been having recently, radiators and air conditioning to keep us at the right temperature all year round, just about any food imaginable within walking distance for most and a life relatively free from rodents and pests to hopefully keep us free from lots of not-so-nice disease-causing bacteria and viruses. It sounds pretty good doesn't it?
What if however I was to suggest to you that our warm, clean, pest-free lives might actually be the cause of some ill-health. That our modern obsession with all things clean and sterile might be counter to what we were originally made for. Would I be spoiling things? Welcome to the hygiene hypothesis and the suggestion that modern health and hygiene might just be too clean.
I am sure that most people will have heard about the hygiene hypothesis in some shape of form. The theory is that our collected efforts to eradicate anything and everything which might not meet with our exacting standards of cleanliness and 'sterility' might actually be putting our immune system in infancy out of a job, with some possible consequences to our health later in life. Whilst the theory remains just a theory, there is some evidence to corroborate this interesting view including some interesting stories about life down on the farm. I was drawn in particular to this recent article and the suggested link between asthma and Helicobacter pylori (also covered here) following my recent posts about asthma and allergy in relation to autism.
The article by Arnold and colleagues looked at exposure patterns to H. pylori in mice and how early exposure to the bacterium seemed to guide immune response to asthma-inducing allergens: the earlier that mice were exposed to H. pylori, the less they reacted to the allergens, a process modified by regulatory T-cells. When I first read this article, the first thing that went through my mind was H. pylori and its relationship to peptic ulcers and that Nobel prize for Medicine awarded in 2005 leading to triple therapy. H. pylori = bad, and eradication of H. pylori = good.
Not so, at least in mice, according to this recent article. I am of course minded to say that correlation does not necessarily imply causation and further replication of the results is required, not least in how such findings relate to humans. I do however appreciate the notion that the various bacteria that traditionally colonised us, having perhaps been modified time after time to survive in places like the human gut, might have quite a lot of effects in relation to health and moderating our risk of things like allergic disease. I partially covered this in a previous post on that lovely helminthic therapy (not for those of a squeamish disposition).
I don't for one minute advocate rolling babies and young children in dirt and detritus or adopting a pet pig just to ensure that they have their full allocated early exposure to bacteria (and viruses) to potentially help with later health. I do however follow the view that children should be allowed to be children; to roll in the short grass being careful of those pesky ticks, make those mud pies and for parents not to be too put off by the appearance of the odd dirty fingernail here and there. Soap and water was good enough for most of us, not forgetting to wash behind the ears. How about a visit to an exhibition on the history of dirt for a real insight?
As if to prove a point, take a look at this young lad from a few years back... I wonder if he ever suffered from an allergy?