Research Suggests Cleanliness Does Not Negatively Impact Childhood Immunity


Researchers seek to reconcile the conflict between necessary cleanliness and exposure to microorganisms for the immune system.

New research points to 4 reasons that clean environments and hygiene may not negatively impact childhood immunity against allergic diseases, according to investigators at University College London.

The “hygiene hypothesis” has been popular for many years and theorizes that early childhood exposure to some microorganisms help provide protection against allergic diseases by strengthening the immune system. However, the researchers said there is a related view that suggests that modern society is too hygienic, meaning young children are less likely to be exposed to these microorganisms.

“Exposure to microorganisms in early life is essential for the ‘education’ of the immune and metabolic systems,” said lead author Graham Rook, MD, BA, MB, in a press release. “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.”

Researchers aimed to reconcile the conflict between necessary cleanliness and exposure to microorganisms for the immune system. According to the press release, they identified 4 factors that suggest cleanliness and immune system development are not mutually exclusive.

Firstly, the authors found that the microorganisms in a modern home are typically not the ones needed for immunity. They added that vaccines significantly help to develop the immune system in addition to providing protection from infections, so exposure to pathogens is less necessary than it would be without vaccines.

Research has also confirmed that the microorganisms found in natural outdoor environments are vital for immune health, so cleaning indoor spaces and personal hygiene have no impact on exposure to natural microorganisms.

Finally, more recent research has found that links between home cleaning and allergies are often not caused by the removal of organisms, but rather by exposure of the lungs to cleaning products. The chemicals in many cleaning products cause lung damage, which encourages the development of allergic responses, according to the study authors.

“So cleaning the home is good and personal cleanliness is good, but, as explained in some detail in the paper, to prevent spread of infection it needs to be targeted to hands and surfaces most often involved in infection transmission,” Rook said in the press release. “By targeting our cleaning practices, we also limit direct exposure of children to cleaning agents.”

Rook concluded that exposure to family members, outdoor environments, and vaccines provide all of the necessary microorganism exposure for childhood immune system development. Exposures such as these are not in conflict with hygiene and cleaning practices.


Being clean and hygienic need not impair childhood immunity. News release. University College London; July 5, 2021. Accessed August 5, 2021.

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