It is a myth that children should be exposed to dirt to avoid a higher risk of allergies, according to a new study.
The hygiene hypothesis had claimed Western society is too hygienic, causing millions of children around the world to suffer from allergies.
But researchers at University College London (UCL) and the London School of Hygiene & Tropical Medicine say where excessive cleaning is to blame it is due to a reaction to certain products, rather than the absence of microbes.
Children are more likely to be exposed to microbes in mud, or through hugging, which prepare their immune systems to fight off dangerous infections.
The paper lists four key reasons to disprove the theory we are "too clean for our own good".
1. Microorganisms found in modern homes are generally not those needed for immunity.
2. Vaccines help to strengthen immune systems, so there is no need to put yourself at more risk by being exposed to dangerous pathogens.
3. New concrete evidence claims microbes from the natural environment are vital to health, and nothing to do with domestic cleaning practices.
4. New research found people with clean homes were more likely to have health issues because their lungs were exposed to the cleaning products, not the removal of bugs.
Lead author, Professor Graham Rook from UCL, noted the paper was meant to deal with the "conflict" between cleaning and the need for microbial inputs for our guts and immune systems.
Professor Rook added: "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."
Exposure to mothers, family members, nature, and vaccines can provide the required inputs, and do not fight off the role of intelligent cleaning, Professor Rook concluded.
The paper was published in the Journal of Allergy and Clinical Immunology.