Origins of Hygiene Hypothesis

A recent NY Times article explains the background of the ‘hygiene hypothesis’ and how it has held up remarkably well as a likely factor in the rising number of allergic and immune-mediated diseases.

Link: Your Environment is Cleaner. Your Immune System Has Never Been So Unprepared

An excerpt:

The British Journal of Homeopathy, volume 29, published in 1872, included a startlingly prescient observation: “Hay fever is said to be an aristocratic disease, and there can be no doubt that, if it is not almost wholly confined to the upper classes of society, it is rarely, if ever, met with but among the educated.”..

In November 1989, another highly influential paper was published on the subject of hay fever. The paper was short, less than two pages, in BMJ, titled “Hay Fever, Hygiene, and Household Size.”

The author looked at the prevalence of hay fever among 17,414 children born in March 1958. Of 16 variables the scientist explored, he described as “most striking” an association between the likelihood that a child would get hay fever allergy and the number of his or her siblings.

It was an inverse relationship, meaning the more siblings the child had, the less likely it was that he or she would get the allergy…The paper hypothesized that “allergic diseases were prevented by infection in early childhood, transmitted by unhygienic contact with older siblings, or acquired prenatally from a mother infected by contact with her older children…

[To avoid disease] we started washing our hands and took care to avoid certain foods that experience showed could be dangerous or deadly…Particularly in the wealthier areas of the world, we purified our water, and developed plumbing and waste treatment plants; we isolated and killed bacteria and other germs…

What does the immune system do when it’s not properly trained?

It can overreact. It becomes aggrieved by things like dust mites or pollen. It develops what we called allergies, chronic immune system attacks — inflammation — in a way that is counterproductive, irritating, even dangerous.

The percentage of children in the United States with a food allergy rose 50 percent between 1997–1999 and 2009–2011, according to the Centers for Disease Control and Prevention…

There are related trends in inflammatory bowel disease, lupus, rheumatic conditions and, in particular, celiac disease. The last results from the immune’s system overreacting to gluten..

And even doctors have been wrong….They have vastly overprescribed antibiotics. These may be a huge boon to an immune system faced with an otherwise deadly infection. But when used without good reason, the drugs can wipe out healthy microbes in our gut.

My take: With the increasing frequency of many diseases, there has to be environmental influences since our population genetic makeup does not change rapidly. Thus factors like infections, microbiome and exposure to antibiotics are likely important in the changing epidemiology.

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