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  • Writer's pictureJoan Rothchild Hardin

The Hygiene Hypothesis

The Hygiene Hypothesis states that being overly afraid of exposure to all kinds of germ and trying to eradicate them completely in our homes is dangerous to our health. Just think of all the products that promise to kill 99% of bacteria!

According to the Hygiene Hypothesis, developing children need exposure to a wide variety of bacteria in order to develop robust immune systems. Young children’s lack of exposure accounts for the steadily increasing incidence of autoimmune diseases in both children and the adults they grow into – including allergies, asthma, skin conditions and many more.

Another way of putting this is that “a lack of exposure to germs in early childhood leads to defects in the establishment of immune tolerance” which we need in order to stay healthy. (Okada et al, 2010)

In what seems to be a paradox, developed countries’ hostility to germs of every kind and consequent over emphasis on absolute cleanliness has caused fragility in our immune systems and rendered them unable to keep us healthy.

According to the Hygiene Hypothesis, the decreasing exposure to germs in Western countries is the source of the increasing incidence of both autoimmune and allergic diseases. Epidemiological data, particularly migration studies, show that subjects migrating from a low-incidence to a high-incidence country develop autoimmune disorders at a high incidence in the first generation.

In a household that’s extremely clean, an infant’s developing immune system isn’t effectively challenged to develop robustly. The immune system of a young child exposed to a wider variety of germs gets ‘educated’ and learns how to launch a defensive response to infectious organisms. Instead, defense responses in the child living in an extremely clean environment are so inadequate that they actually contribute to the development of autoimmune conditions like asthma and allergies. (US FDA, 2018)

The name Hygiene Hypothesis may be confusing because it seems to refer to personal cleanliness Not so. The Hygiene Hypothesis does not suggest that giving up showering is a good thing. “Reducing personal hygiene, such as not washing hands before eating, is expected to simply increase the risk of infection without having any impact on allergies or immune disorders”. (Wikipedia, 2/14/2021)

Do however stay away from antibacterial soaps, mouthwashes and toothpastes. They kill our protective, probiotic bacteria along with any illness-inducing ones so do serious damage to the bacterial microbiomes found on your skin and inside your mouth.

A short video explaining the Hygiene Hypothesis:


Okada, H, Kuhn , C, Feillet, H & Bach, J-F. (April 2010). The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update. Clinical Experimental Immunology, 160:1, 1-9. See:

US FDA. (3/23/2018). Asthma: The Hygiene Hypothesis. See: See:

Wikipedia. (2/14/2021). Hygiene Hypothesis. See:

© Copyright 2021. Joan Rothchild Hardin. All Rights Reserved.

DISCLAIMER: Nothing on this site or blog is intended to provide medical advice, diagnosis or treatment.


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