This is the first study to directly evaluate this issue. From this study Erika von Mutius, a highly respected researcher in this field, concludes – No. “Development of allergies and asthma was not related to cleaning activities”.
She explains “The so-called hygiene hypothesis is still widely accepted in the public domain to explain the rapid rise in allergic disorders in affluent populations. Originally conceived as a lack of infections predisposing to allergies, the hygiene hypothesis is still often reduced to concepts such as ‘eat dirt’, ‘too clean is bad’, or ‘sterile homes’. To a lay audience, the U.S. Food and Drug Administration explain the hygiene hypothesis in terms of ‘the extremely clean household environments often found in the developed world’.” What is overlooked is the fact that the relationship between household or personal cleanliness and development of allergies has never been properly investigated or established.
Methods: Questionnaire information on home or personal cleanliness and allergic health conditions at school age was collected in a birth cohort of 399 participant families. Bacterial markers were measured in floor and mattress dust, whilst standards of home and personal cleanliness. Cleanliness variables were tested against dust markers and the protective effects of dust markers on asthma and allergic conditions confirmed.
Results and conclusions: Bacterial exposure in house dust was found to be associated with reduced risk of childhood asthma and allergies whilst personal cleanliness, such as washing hands, and home cleanliness were objectively reflected by dust parameters in homes. However, neither personal nor home cleanliness were associated with protection from asthma and allergies.
Mutius et al state “Recontamination by hands, skin, or textiles leaves conventional cleaning a Sisyphean labour and dismisses the idea of ‘excessive cleanliness’ and ‘sterile homes’ as a cause of allergy.
Note: Although results suggest that cleanliness does not impact on development of asthma and allergies, in this study, cleanliness was measured by objective, but rather unspecific dust measurements. The findings suggest that allergy protection operates through as yet unknown microbial exposures, which cannot accurately be assessed by unspecific markers. Future studies will require more in depth investigations of microbial exposure. Whether these are affected by cleaning activities remains to be elucidated; the findings with unspecific markers, however, suggests that normal cleaning does not affect permanent microbial colonization of indoor environments.
The study can be found at: Am J Respir Crit Care Med. 2015 Jan 13. [Epub ahead of print] Asthma and the Hygiene Hypothesis – Does Cleanliness Matter? Weber J, Illi S, Nowak D, Schierl R, Holst O, von Mutius E, Ege MJ.