Statistics Seems To Support The Hygiene Hypothesis

Several epidemiological studies have investigated the protective effect of infectious agents in allergic and autoimmune diseases. The existence of one or more older siblings protects against development of hay fever and asthma, of multiple sclerosis and also of Type 1 Diabetes, as does attendance at day care during the first 6 months of life in the case of atopic dermatitis and asthma.

Interestingly, exposure to farming and cowsheds early in life prevents atopic diseases, especially if the mother is exposed during pregnancy.

However, these data have been contradicted by other studies showing an increased prevalence of asthma correlated with higher levels of endotoxins in urban housing. The level of endotoxins is higher in farms as compared to cities, and subjects are in contact with a greater variety of microbial compounds in farms, which could explain this discrepancy.

Genetics and other factors can play their role too

It is important, though, to not forget about the genetic factors. Recent studies have shown that an individual’s response to environmental and microbial exposures is partially dependent on his/her genetic make-up (usually referred to as genetic polymorphism in scientific literature). The genetic polymorphism is linked to the altered immune responses to various environmental stimuli. So while the influence of external factors is undeniable, it is impossible to ignore the important role of our genetic code in the development of immune system-related medical problems.

But despite the fact that several detailed reviews of studies of the hygiene hypothesis have been published in recent years, the studies have persistent limitations. Cross-sectional studies of this subject are intrinsically retrospective over very long periods of time and are therefore subject to a significant recall bias. In addition, lack of easy to get medical records can mask essential differences between subjects and controls – something which is quite likely to happen in the third world countries with limited budgets. Many of the factors studied are interrelated and impossible to separate properly.

So does excessive hygiene bring harm?

The hygiene hypothesis originated from epidemiological observations relating exposure to other children to a reduced risk of allergy. Studies are still in progress in a number of laboratories worldwide to try and explain this hypothesis.

See Also: Nine Ways Oral Hygiene Helps Keep Your Body and Mouth in Connection

Undeniable fact of life is that without some degree of exposure to the dangerous environmental elements our immune system simply cannot be trained to recognize them. At present, the medical science has not progressed far enough to make the immune system to recognize and eliminate any possible dangerous environmental elements from the body. As a result, some doctors would argue against the excessive cleanliness so often practiced by young mothers. However, we still need to see the solid undeniable evidences that such practice is harmful. In their absence, the hygiene hypothesis remains an interesting but still controversial point of view.