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Being clean and hygienic need not impair childhood immunity

5 July 2021

The theory that modern society is too clean, leading to defective immune systems in children, should be swept under the carpet, according to a new study by researchers at 香港六合彩中特网 and the London School of Hygiene & Tropical Medicine.

Child sweeping alongside man wiping floor with cloth

In medicine, the聽鈥榟ygiene hypothesis鈥櫬爏tates that early childhood exposure to particular microorganisms protects against聽allergic聽diseases by contributing to the development of the聽immune system.

However, there is a pervading view (public narrative) that Western 21st century society is too hygienic, which means toddlers and children are likely to be less exposed to germs in early life and so become less resistant to allergies.

In this paper, published in the聽Journal of Allergy and Clinical Immunology, researchers point to four significant reasons which, they say, disprove this theory and conclude we are not 鈥渢oo clean for our own good鈥.

Lead author, Emeritus Professor of Medical Microbiology Graham Rook (香港六合彩中特网 Infection & Immunity), said: 鈥淓xposure to microorganisms in early life is essential for the 鈥榚ducation鈥 of the immune and metabolic systems.聽

鈥淥rganisms that populate our guts, skin and airways also play an important role in maintaining our health right into old age:聽so throughout life we need exposure to these beneficial microorganisms, derived mostly from our mothers, other family members and the natural environment.聽

鈥淏ut聽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.聽聽

鈥淚n this paper, we set out to reconcile the apparent conflict between the need for cleaning and hygiene to keep us free of pathogens, and the need for microbial inputs to populate our guts and set up our immune and metabolic systems.鈥

In a review of evidence, the researchers point to four factors.

  • Firstly, the microorganisms found in a modern home are, to a significant degree, not the ones that we need for immunity.
  • Secondly, vaccines, in addition to protecting us from the infection that they target, do a lot more to strengthen our immune systems*, so we now know that we do not need to risk death by being exposed to the pathogens.
  • Thirdly, we now have concrete evidence that the microorganisms of the natural green environment are particularly important for our health; domestic cleaning and hygiene have no bearing on our exposure to the natural environment.聽聽
  • Finally, recent research** demonstrates that when epidemiologists find an association between聽cleaning the home and health problems such as allergies, this is often not caused by the removal of organisms, but rather聽by exposure of聽the lungs to cleaning products that cause a type of damage that encourages the development of allergic responses.

Professor Rook added: 鈥淪o 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. 聽By targeting our cleaning practices, we also limit direct exposure of children to cleaning agents

鈥淓xposure to our mothers, family members, the natural environment, and vaccines can provide all the microbial inputs that we need.聽聽These exposures are not in conflict with intelligently targeted hygiene or cleaning.鈥

*听聽Lancet Infectious Diseases 2020

**听. Cell 2021

**听聽Nature Reviews Immunology 2021

Links

  • Read the paper in the Journal of Allergy and Clinical Immunology:
  • Academic profile:

Image

  • 鈥楶hoto of man cleaning the floor鈥. Credit: Gustavo Fring via [CC BY 2.0]

Further information