The Hygiene Hypothesis
The Hygiene Hypothesis has been around a while. Dr. David P. Strachan wrote about it first in 1989 in an article in the British Medical Journal. He proposed the hypothesis to explain the observation that allergic diseases, such as hay fever and eczema, were less common in children growing up in larger families. The explanation for this observation says that some exposure to infectious agents during childhood helps develop a robust and healthy immune system and that children in larger families are exposed to more infectious agents through their siblings.
Since that time, the Hygiene Hypothesis has been studied in great detail. It now is often mentioned to explain the general increase in allergic diseases since industrialization and the higher rate of allergic diseases in developed countries.
A recent study funded by the JDRF has found “common intestinal bacteria may somehow interact with the early (innate) immune system to modify type 1 diabetes risk, a finding that supports the hygiene hypothesis.” You can read the synopsis published by the JDRF here:
JDRF-Funded Study Links “Hygiene Hypothesis” To Diabetes Prevention
Wikipedia has a great article on the Hygiene Hypothesis, including cross-references and alternative hypotheses.
