There is a very interesting theory in immunology: the hygiene hypothesis. Basically, if you are too clean and not exposed to enough dirt, scum and bacteria...you will suffer eventually. Our immune system has evolved to detect, recognize and eliminate millions of different molecular structures found among other things, on viruses and bacteria. Early exposure seems to be a key to a healthy immune system and a allergy-free life. This is, once more, confirmed by a new study published today (Sept 22nd, 2008) Clinical and Molecular Allergy. Fecal samples collected from 21 infants showed that a poorly diverse gut microbiota is associated with eczema development early in life.
"We found a significant inverse association between fecal bacterial diversity and eczema in early life. In addition, we found a significant increment in fecal bacterial diversity from ages 1 to 4 months in healthy children, but not in children who developed eczema by age 6 months."
To understand these findings, it is important to realize that our immune system is often "educated" through the gut, in fact more than 70% of the immune system is gut-associated. Experimental mice models show that a sterile gut leads to an abnormal immune system geared towards the development of allergies. In their article, the authors mention a reduced microbial diversity has also been implicated in various diseases including Crohn's disease and coeliac disease.
Click HERE to find a .pdf version of this very interesting article