Can you be too clean?

The ‘hygiene hypothesis’ may continue to stick in the mind for some, but it is outdated.

In its place is the ‘old friends’ hypothesis, proposed in 2003. The ‘old friends’ hypothesis focuses on the importance of exposure to non-pathogenic commensal microorganisms to good immune function, especially in early life. And removes the focus on hygiene, which is as important as ever in preventing the spread of infectious disease.

Non-pathogenic commensal microorganisms…what?

Pathogenic microorganisms: disease-causing microorganisms. BAD.

Commensal microorganisms: microorganisms that live on the body and help maintain human health (also known as normal microflora). GOOD.

Fun fact: the human body contains 10x more microorganisms than human cells!

A 2016 paper¹ emphasised the need to ditch the term ‘hygiene hypothesis’. This paper called for ‘targeted hygiene’, amongst other strategies,² to maximise ‘protection against pathogen exposure while allowing spread of essential microbes between family members’.

‘Targeted hygiene’? In other words, cleaning and disinfecting at specific times and places to reduce the risk of exposure to harmful microorganisms. As opposed to fanatically removing every speck of dirt or using antibacterials indiscriminately all over your house.

Little was known about disease transmission until the 1800s, when scientists discovered that microorganisms caused issues like food spoilage. This led to an understanding of hygiene’s vital role in preventing the spread of pathogens.

Improved hygiene has since played a role in reducing infectious diseases. Think of the COVID-19 pandemic. Public health messages emphasised handwashing and cleaning high-touch surfaces to prevent the disease from spreading. These practices are also effective against illnesses such as flu, RSV and bacterial infections.

Maintaining good hygiene at home is key to preventing the spread of disease-causing organisms between family members.

So, even if living more sanitarily has contributed in any small way to an increase in allergies and autoimmune diseases, think of the alternative. Infectious disease deaths have declined by over 98% from 1907 to 2020 in Australia,³ it would be sad to reverse that trend.