A pandemic problem: Too much cleaning is bad for your health

Sterilising surfaces will have damaged microbiome biodiversity, essential for health

We will long remember all the precautions we took, and are still taking, to avoid contracting Covid-19: social distancing, face masks, sanitising hands and surfaces, avoiding crowds, no hugging and kissing, and more.

But this pandemic will pass, and we must then return to normal pre-Covid-19 social interactions for the sake of our physical and mental health. However, some public health professionals worry that many people have now been trained to fear the world so much they will continue to take precautions that will be not only be unnecessary but actually harmful when this pandemic has passed (James Hamblin, the Atlantic).

We need close personal contacts with others and with the surrounding physical world in order to maintain good health. Our physical bodies – head, trunk, arms, legs, internal organs – don’t describe us completely because we each also live in symbiosis with a vast invisible accompanying world of microbes, including bacteria, fungi and viruses.

This vast hidden microbe ecosystem is called the microbiome, and it has co-evolved with human beings for many thousands of years. A dense concentration of microbes, mainly bacteria, populates the human gut, and microbiome organisms also populate our skin, lungs and elsewhere. Scientific study of the microbiome is new, and most publications on the subject have come out only in the past 10 years.


Much remains to be discovered but it is already clear that the microbiome closely influences human health. A healthy, diverse microbiome correlates with good health, and a compromised microbiome correlates with poor health.

Although some microbes are harmful, such as the annual flu virus and the Covid-19 coronavirus, the great majority of microbes we come in contact with are either harmless or actually good for us, and we need “good” microbes in our microbiome for good health. The microbiome is involved in many processes of fundamental importance, such as helping to train the immune system and to digest our food, synthesising vitamins K and B in the gut and much more.

Early setback

The composition of our microbiome fluctuates mildly as we are exposed to other microbes in our daily lives. If we are deprived of these exposures, especially at the start of life, our immune system will be prone to malfunction, possibly resulting in allergies, asthma, autoimmune disorders, obesity, type 2 diabetes and other chronic conditions.

Over the past decade, microbiologists have grown concerned about excessive use of antibiotics and sanitisation of the environment. Antibiotics are a great boon to medicine in fighting disease but they are very often overused and/or inappropriately used.

Both antibiotics and sanitising surfaces kill microbes and together can force “good” microbes, needed for healthy microbiomes, into extinction. And, of course, during the past year we dramatically intensified our focus on hand and surface sanitisation and avoiding exposure to viruses. We can expect that these various pressures have significantly diminished microbiome diversity.

The microbiomes of the very young and of the elderly are the most labile, whereas microbiomes in older children and adults are resilient and any damage done during the pandemic can be easily reversed. High-fibre diet, spending lots of time outdoors, contact with animals and, of course, getting back to normal life when safe to do so, mixing freely with others and hugging and kissing loved ones, are all very good for improving microbiome diversity. Vaccinating the over-70s first was very important to allow them to re-establish normal microbiomes through earlier access to visitors and open areas. And breastfeeding infants is very good for setting up a healthy microbiome.

Surface transmission

Re-establishing normal social contacts when we are all vaccinated and this pandemic is over will be important, although taking extra precautions during flu season would be helpful. If you are nervous, remember the implications of clinging on to the old pandemic precautions, particularly sterilising our surroundings. The risk of surface transmission of Covid-19 is less than one 10,000.

Before the Covid-19 pandemic only one of the top-10 causes of death, influenza, was attributable to an infectious disease that you could catch. Nearly all the other causes of death – heart disease, stroke, cancer, diabetes and so on – correlate with unhealthy microbiomes. So, when we get the signal from health officials to resume normal life let us mingle with each other again – we have nothing to lose but our masks.

William Reville is an emeritus professor of biochemistry at UCC

William Reville

William Reville

William Reville, a contributor to The Irish Times, is emeritus professor of biochemistry at University College Cork