What really is cleaning’s relationship with immunity?

It has been posited in the past that overly enthusiastic cleaning can threaten immunity against disease; that over-protecting people, particularly children, can prevent the necessary build-up of antibodies against infectious illness. There is a theory that exposure to germs is helpful, even necessary, for a robust immune system.

The ongoing COVID-19 pandemic and the way in which cleaning and disinfection has shifted as a result of the last 16 months has placed a renewed spotlight on that hypothesis.

Is the world becoming “too” clean?

Not so, according to new research.

A study published in The Journal of Allergy and Clinical Immunology and conducted by researchers at University College London (UCL) and the London School of Hygiene and Tropical Medicine countered that theory with four key conclusions:

1. Most of the microorganisms found in a home, school, or other building are not the ones that humans need for immunity.
2. In addition to protecting individuals from the infection that they target, vaccines help strengthen people’s immune systems. Therefore, people do not need to risk death by being exposed to dangerous pathogens.
3. Concrete evidence now exists that the microorganisms found in the natural environment are particularly important for human health. Domestic cleaning and hygiene have no bearing on people’s exposure to that natural environment.
4. Recent research demonstrates that when epidemiologists find an association between cleaning and health problems, such as allergies, this is often not caused by the removal of organisms but rather by exposure of the lungs to excess cleaning chemicals.

“Exposure to microorganisms in early life is essential for the ‘education’ of the immune and metabolic systems,” said Graham Rook, study lead author and professor at UCL. “Organisms that populate our guts, skin, and airways also play an important role in maintaining our health right into old age: so throughout life we need exposure to these beneficial microorganisms, derived mostly from our mothers, other family members and the natural environment.

“But for more than 20 years there has been a public narrative that hand and domestic hygiene practices, that are essential for stopping exposure to disease-causing pathogens, are also blocking exposure to the beneficial organisms.”

Diligent home cleaning won’t remove beneficial microorganisms

The key takeaway from the study was that cleaning in the home and maintaining proper hygiene does not affect immunity by limiting exposure to the natural environment and its beneficial microorganisms. Recent research shows that cleaning the home also does not have a connection to allergies because of the removal of organisms.

“Cleaning the home is good, and personal cleanliness is good, but to prevent the spread of infection, it needs to be targeted to hands and surfaces most often involved in infection transmission. By targeting our cleaning practices, we also limit direct exposure of children to cleaning agents,” Prof. Rook adds. “Exposure to our mothers, family members, the natural environment, and vaccines can provide all the microbial inputs that we need. These exposures are not in conflict with intelligently targeted hygiene or cleaning.”