The child’s immune system needs contact with microbes to exercise and to prevent allergies – too much hygiene and cleanliness are therefore harmful to children, is a common assumption. Thorough cleaning in the household and measures against pathogens such as regular hand washing do not in principle contradict contact with beneficial organisms, two researchers now write in a review article in Journal of Allergy and Clinical Immunology. It depends on a targeted approach.
The reactions of many people in the corona pandemic showed that the line between sensible cleanliness and excessive measures is not clear to everyone, write Graham Rook from University College London and Sally Bloomfield from the London School of Hygiene and Tropical Medicine. Instead of concentrating on measures such as regular hand washing, not touching the face and keeping your distance, particularly intensive floor cleaning would be practiced. This could have consequences, especially for children, but also for the health of adults.
The increased occurrence of chronic inflammatory diseases such as allergies, autoimmunity and inflammatory bowel diseases in societies with a western lifestyle is at least partially due to impaired immune regulation. There are suspicions that this is due to a “distortion of microbial input in early life due to domestic hygiene practices”. At the same time, hygiene at home and in everyday life is essential to protect against dangerous pathogens.
In the early humans who lived in caves and later in the simple houses made of straw, wood, clay or stone plastered with earth, clay or animal dung, the microbes living in them did not yet differ significantly from those in the natural environment, write Rook and Bloomfield . Modern houses, however, housed microorganisms in a completely different composition than in nature. “This difference is made worse when the house is in the city and far from nature.”
It is important to have contact with natural microorganisms outside, not in the house
There are now concrete indications that microorganisms in the natural green environment are particularly important for health. The cleaning and hygiene at home have little influence on the contact with these microbes outside.
In turn, some of the immunoregulatory mechanisms are not due to certain types of microbes, but to common microbial components such as so-called muramic acid derivatives. According to one study, such compounds are linked to protection against allergies in children. Cleaning will reduce the amount a child is exposed to at home, but not to ineffective levels. Neither hygiene measures such as hand washing and washing of towels nor domestic and personal cleanliness had an influence on the development of allergic diseases in this study.
The experts also cite research results that show that the connection between home cleaning and health problems such as allergies can often be traced back to repeated contact with cleaning agents. Regular use of quaternary ammonium compounds is also associated with problems such as asthma. In addition, many products contained potential allergens such as enzymes. In principle, cleanliness at home and personal hygiene are good, but the correct and targeted use of the products should be ensured in order to limit the exposure of children to cleaning agents.
Cleaning and hygiene that focuses on crucial aspects is therefore not in conflict with a health-related examination of certain microbes from the natural environment or from parents and other family members. Washing fruit and vegetables as well as hand washing after going to the toilet or before touching food is crucial in order to prevent intestinal infections. Garbage, pets and surfaces that have been touched by many people are also potential sources of pathogens and thus cause people to wash their hands.
In contrast, floors and surrounding areas in the domestic area are to be regarded as low-risk with regard to the transmission of infections, they are rarely contaminated with harmful microbes and usually no critical contact points. It is not useful or even harmful to sterilize such areas or even to spray open areas and certain areas in buildings – such as underground stations – with disinfectants.