(Image credit: Getty Images)
Many of us spring clean as the weather warms up. But is there such a thing as house that’s too clean? Could a little bit of dirt be good for us?
With spring around the corner in the Northern Hemisphere, many of us are ready to open the windows, get out the cleaning products and remove all the dust, grime and dirt in our homes.
But how important is having a clean home for our health? Does deep cleaning help prevent infection and protect us from diseases? Experts say we should be careful not to conflate cleanliness with good hygiene.
The Covid-19 pandemic increased household cleaning as people tried to keep the virus at bay by disinfecting every inch of their home. This was exacerbated by the World Health Organization warning early on that the virus could spread through contaminated surfaces, known as fomites. Later research concluded that surfaces presented a low risk of disease transmission.
Sally Bloomfield, chairperson of the International Scientific Forum on Home Hygiene and an honorary professor at London School of Hygiene and Tropical Medicine worries the pandemic has led many people to pick up unhelpful cleaning habits. These can include such things as obsessively scrubbing their floors, instead of focusing on good hygiene practices which help prevent the spread of disease.
“People have an obsession with cleanliness as a means to protect themselves against germs,” says Bloomfield. “It’s somewhere in our DNA that we associate cleanliness with health… We’ve evolved to have a disgust reflex and avoid things that are nasty or smelly.”
But cleanliness and hygiene are not the same thing, she says.
Current health advice suggests people should clean their hands after handling pets, for instance (Credit: Getty Images)
“Cleanliness is about achieving the appearance of [an area] looking clean, through vacuuming or wiping it,” she says. “But hygiene is about protecting yourself from harmful microbes.”
These include pathogens such as norovirus, flu, Covid-19 and salmonella, says Bloomfield.
“Hygiene is a set of actions, not a state, which you carry out when it’s necessary, rather than at a prescribed time,” says Bloomfield. “It’s about intervening at key moments.”
We should all practice “targeted hygiene” in our daily lives and recognise when harmful microbes are likely to spread, says Bloomfield. For example, when we’re handling raw food, using the toilet, touching pets, blowing our nose or disposing of rubbish.
Nine key moments for targeted hygiene
The International Scientific Forum on Home Hygiene has set out nine key moments when it is vital that we practice good hygiene in our daily lives:
● During food handling
● While eating with fingers
● Using the toilet and changing a nappy
● Coughing, sneezing and nose blowing
● Touching surfaces frequently touched by other people
● Handling and laundering “dirty” clothing and household linens
● Caring for domestic animals
● Handling and disposing of refuse
● Caring for an infected family member
The belief that cleanliness and hygiene are the same has persisted since the late 1980s, when epidemiologist David Strachan postulated the hygiene hypothesis. It argued early childhood exposure to germs and infections helps develop children’s immune systems and protects against allergies.
The rise in childhood allergies and asthma in the late 20th Century was linked to children’s reduced exposure to microbes through declining family sizes, limited interaction with animals and higher standards of cleanliness, according to Strachan.
But scientists now argue that there is no evidence showing that cleanliness is linked to the development of allergies.
Graham Rook, emeritus professor of medical microbiology at University College London (UCL), says the hygiene hypothesis should instead be reframed as the “old friends hypothesis.” He argues that exposure to “old friends”, non-infectious organisms, which have been around for much of our evolutionary history, is actually what trains the immune system to not overreact to harmless microbes, rather than childhood infections or how clean your home is growing up.
Since the 1980s, some scientists have believed playing in dirtier environments helps create a healthy immune system in children (Credit: /Getty Images)
We’re born with a fully formed immune system that needs programming,” says Bloomfield. “The programming is done by the ‘old friends’. [They are] teaching the immune system to not react to things like pollen and food allergens, which are perfectly harmless.”
A child’s susceptibility to developing allergies therefore does not have anything to do with cleanliness, but rather with their exposure to different types of microorganisms via their gut, their skin and the air they breathe, according to scientists. (Read more about how we can prevent food allergies through early exposure.)
In a 2021 study, Rook and Bloomfield concluded that we are not too clean for our own good.
Children receive all the microbial inputs they need to develop a healthy immune system through vaccines, their natural environment and the beneficial microbiota they derive from their mothers during childbirth, they said.
“We definitely do need to encounter the microbiota from our mothers, and from the natural environment, and a failure to do so certainly contributes to immunoregulatory disorders such as allergies because these organisms set up the mechanisms that regulate the immune system,” says Rook. But cleaning the home “does not necessarily reduce the child’s exposure to mother or to nature”.
“Targeted hygiene practices at key risk moments and sites can maximise protection against infection while minimising any impact on essential microbial exposures,” the study states.
“You cannot keep your home hygienic. If you wanted to do that, you would have to put it in a sterile box,” says Bloomfield. “But if you intervene at key moments, you will deal with most of the risks.”
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