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The hygiene myth

It is generally assumed that being as clean as physically possible is a good thing. But then again you often hear stories of microorganisms developing resistance to antibiotics, of children who are never exposed to germs not developing a great immune system. In this article CHT asks if there really is such a things as being too clean

Before we go any further, maybe we should discuss the term “atopic allergy”. Atopy is a predisposition toward developing certain allergic reactions or hypersensitivities. In short experts had noticed that since 1950 the amount of allergies being reported amongst children had risen to unheard of levels. According to Heather Fraser’s book The Peanut Allergy Epidemic the number of children in the UK and the US with an allergy to peanuts went from 416,000 to 4,500,000 in the space of 12 years (1997-2009).

Indeed allergyuk.org claims that: “This increase was initially seen in countries such as the UK, Europe and USA, but can now be found in all countries undergoing industrial development. The pattern of allergy is also changing – initially, the increase was in asthma and allergic rhinitis (hay fever). However, recent studies have confirmed a significant increase in the incidence of food allergies, in particular amongst children. In the UK, it is estimated that up to 50 per cent of children are diagnosed with an allergic condition.”

An allergy is when the body’s immune system reacts strangely to an actually harmless substance such as pollen, dust or nuts. Still according to allergyuk.org one in five UK children have an allergic predisposition, however if your mother has an existing allergy the risk is doubled. We also know that children with regular contact with farm animals have a lower incidence of allergy.

THE HYGIENE HYPOTHESIS
iStock_000002220137LargeBut why is all of this happening? Some experts think it might be explained by something called the Hygiene hypothesis. The Hygiene hypothesis suggests that:

“A lack of early childhood exposure to infectious agents, symbiotic microorganisms (such as the gut flora or probiotics) and parasites increases susceptibility to allergic diseases by suppressing the natural development of the immune system.”

It arose in 1989 when David Strachan proposed that the virtual eradication of infection in children’s formative years might explain why the number of people suffering from asthma and hay fever exploded in the the second half of the 20th century.

In short the hypothesis states that the revolution in cleanliness in the 19th century meant that young children were no longer exposed to cholera, typhoid or other similar diseases to anything like the degree they had been in the past. As such their immune systems didn’t develop fully. In 2003 Graham Rook proposed that young humans need to be exposed to the same diseases our evolutionary ancestors were in order to develop properly functioning immune systems. In short this meant any diseases that could profligate. Though we are primarily concerned with infections here it has also been suggested that auto-immune diseases (Lupus et al) and certain types of Leukemia might be attributed to the same phenomenon. Of course hygiene and cleanliness are far from the only factors in contracting these conditions, but Strachan’s hypothesis has certainly gained traction.

STUDIES
Since the original hypothesis was proposed a whole host of studies and theories developed the underlying idea and, depending where you look, you can find a plethora of opinion to support either side.

The International Scientific Forum on Home Hygiene (IFH) studied over 20 years’ of scientific data and concluded that the idea that people are living in “too clean” environments is patently absurd. Infections are still rampant in the UK, around 17 million people in the UK each year get a stomach bug. This corresponds to to about 19 million days off work or school. This is just stomach bugs. Colds, flu and a whole host of similar illnesses will take a similar toll.

iStock_000010781808LargeThey concluded the problem wasn’t actually eradicating harmful microbes that cause illness, but the friendly ones our immune systems evolved with back in the stone age. Some scientists suggest that rates of illness and allergic reactions have actually been increasing for centuries, if not millennia, it is only in the last five decades that we have started to notice. They say that far from new causes of allergies arising it might just be down to better diagnostic tools being developed.

Since the early 1800s humanity has introduced clean drinking water, more hygienic food, sewer systems and modern medicine. This has had very beneficial, tangible effects. But, whilst helping they may also have caused unforeseen problems by altering our relationship with the “microbrial” world.

Also modern environments, homes and offices, gyms and transport systems will have far fewer types of microbes than they would have done a couple of hundred years ago. Some have also suggested that moving away from “traditional” human environments like farms means we are having to adapt to an entirely new type of threat. The microbes from urban areas are entirely different from those found in rural environments. It doesn’t matter how clean you think your home is…. Even immaculate properties are abound with bacteria, viruses, fungi, moulds and dust mites.

One of, if not the, most consistent finding is that children who grow up on a farm, in close proximity to animals are far less likely to develop allergies or asthma.

A quick online search will develop two camps, those who think that they Hygiene hypothesis is valid and those who think it isn’t. In fact some scientists have conducted studies that found a link between the vegetation you grew up around and the likelihood you would grow up allergic to something.

Happily most seem to think that the fact that humanity has eradicated so many diseases doesn’t mean we have to abandon modern medicinal and cleaning techniques. Indeed as we lose trust in antibiotics, move around the globe more freely and as our population gets older we learn more and more how important cleaning and hygiene is to not just businesses but humanity in general.

THE FUTURE
That being said none of us should get to complacent. Gov.uk boasts a reports entitled: “Foresight. Infectious Diseases: preparing for the future. Executive Summary. Office of Science and Innovation, London (2006).”

Produced by the UK Government’s Foresight project: Infectious Diseases: preparing for the future. They say that it is of interest to: “Policy makers concerned with infectious diseases in humans, animals and plants. It will also be of interest to a wide range of disease management professionals, people in industry and business, and researchers in natural and social sciences. The report takes an international perspective and will therefore be of interest to governments and non-governmental organisations across the world.”

SIR DAVID KING KB SCD FRS
Chief scientific adviser to HM Government, and head of the Office of Science and Innovation commented: “Firstly, infectious diseases are diverse and dynamic; new outbreaks occur frequently and we are discovering new infectious agents year on year. This argues the need for policies that are flexible in relation to an evolving threat, and which can address a wide spectrum of possible diseases.

“Secondly, new detection, identification and monitoring systems could provide a step-change in our capability to manage diseases in the future. However, this potential will only be realised if the deployment of the new systems takes careful account of local systems of culture and governance, and provided the systems are integrated with effective control measures.”

About Sarah OBeirne

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