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Hygiene in the Industrial World:
An Unhealthy Obsession with Cleanliness?

(Released June 2011 2011)

podcast link 
  by Kathryn Mori & Carolyn Scearce  


Key Citations





Human Health and the Problem of Uncertain


In the context of modern medical research, it is often difficult to determine the best choices for protecting the health and well being of ourselves and our loved ones. As in the case of the hygiene hypothesis, we are frequently presented with tantalizing glimpses into the factors potentially affecting human health but offered no definitive answers. Ultimately, the current state of medical knowledge does not offer irrefutable proof regarding which versions, if any, of the various sub-hypotheses associated with the hygiene hypothesis give the most accurate information regarding how to protect and maintain human health.

There are many difficulties regarding epidemiological studies that make it difficult to identify the ultimate causes of human diseases or other factors impacting human physiology. There are a number of reasons that this is so. For one thing, many diseases can be affected by a variety of genetic and environmental factors. Also, it is extremely difficult to perform controlled studies on human populations. Human subjects may submit to health studies, but they are frequently short in duration and limited in the scope of factors that they can account for. For practical, ethical, and behavioral reasons, it is impossible to control or even completely identify the multitude of everyday factors that influence an individual’s state of health.

The results of a survey of asthma prevalence in the U.S
The results of a survey of asthma prevalence in the U.S. from the National Center for Health Statistics, Centers for Disease Control and Prevention

Epidemiologists rely heavily on tools such as questionnaires, which are not always completely accurate. When people are questioned about their medical histories they may not remember correctly, or purposely conceal information they feel uncomfortable revealing. Also, epidemiology relies heavily on statistics. Statistics may be good at revealing correlations between multiple data sets, but correlation does not always point clearly to causality. For instance, Strachan's initial study for the hygiene hypothesis was able to uncover a correlation between increased incidents of allergies in smaller families but the cause of this relationship was a matter of speculation. As the original hygiene hypothesis suggests, insanitary contact between children may help strengthen a child's immune system. However, it is also possible that the size of the family is merely related to some other factor in modern lifestyle that actually leads to increased allergy rates.       
Given the current state of uncertainty regarding the hygiene hypothesis and its multitude of variations, no individual course of action seems readily available to best optimize human health. In fact, some versions of the hygiene hypothesis suggest that the best means of decreasing inflammatory conditions is by exposing young children to dangerous bacterial and viral infections or by exposing adults or children to intense parasitic infections. If such is the case, it may be that the cure is potentially worse than the disease. Should further research convincingly demonstrate such extreme measures are necessary to treat these conditions, it may be medically expedient to follow such a course of action for extreme suffers. However, such therapies would require very close medical supervision to manage the risks involved. Since such extreme measures have yet to be shown to provide the best course of action, it is unlikely that many physicians would be inclined to advocate or even monitor such potentially risky courses of action.

On the other hand, the hope of promoting a more positive state of health is associated with some of the more moderate versions of the hygiene hypothesis. If it is true that the immune system can be primed by a consortium of non-pathogenic bacteria, then fairly simple and much less risky changes in behavior may be able to do much to decrease the incidence of inflammatory disorders. It may be that choices such as being less preoccupied with sterilizing the objects that infants come in contact with or making sure that young children come in frequent contact with other children of a similar age may improve overall health later in life. Other factors such as encouraging children to play outdoors or introducing them to healthy domesticated animals may also be beneficial. Additional factors could involve being vigilant in ensuring that people are not given unnecessary antibiotics and promoting less refined diets that are rich in prebiotics and probiotics.          

There is no certainty that these changes in behavior will prevent a person from developing allergies, or even reducing the severity of allergies. Even if these are the factors that are associated with the development of allergies, epidemiology addresses statistical trends and not how a single person will respond to individual genetic, environmental, or lifestyle factors. Even in undeveloped countries there are some people who still show allergy symptoms. There is still a lot to be learned about allergies and other inflammatory conditions and how individual biological factors influence the level of incidence. The high rate of variation of allergies from one country to another does suggest that environmental and/or lifestyle choices may have a significant impact on the frequency and intensity of allergies. However, there also seems to be a significant genetic component, and for a segment of the population, allergies may currently be unavoidable.

© 2011, ProQuest LLC. All rights reserved.

List of Visuals

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