title: Time to abandon the hygiene hypothesis: new perspectives on allergic disease, the human microbiome, infectious disease prevention and the role of targeted hygiene.
abstract: OBJECTIVE
  To review the burden of allergic and infectious diseases and the evidence for a link to microbial exposure, the human microbiome and immune system, and to assess whether we could develop lifestyles which reconnect us with exposures which could reduce the risk of allergic disease while also protecting against infectious disease.
  
  
  METHODS
  Using methodology based on the Delphi technique, six experts in infectious and allergic disease were surveyed to allow for elicitation of group judgement and consensus view on issues pertinent to the aim.
  
  
  RESULTS
  Key themes emerged where evidence shows that interaction with microbes that inhabit the natural environment and human microbiome plays an essential role in immune regulation. Changes in lifestyle and environmental exposure, rapid urbanisation, altered diet and antibiotic use have had profound effects on the human microbiome, leading to failure of immunotolerance and increased risk of allergic disease. Although evidence supports the concept of immune regulation driven by microbe-host interactions, the term 'hygiene hypothesis' is a misleading misnomer. There is no good evidence that hygiene, as the public understands, is responsible for the clinically relevant changes to microbial exposures.
  
  
  CONCLUSIONS
  Evidence suggests a combination of strategies, including natural childbirth, breast feeding, increased social exposure through sport, other outdoor activities, less time spent indoors, diet and appropriate antibiotic use, may help restore the microbiome and perhaps reduce risks of allergic disease. Preventive efforts must focus on early life. The term 'hygiene hypothesis' must be abandoned. Promotion of a risk assessment approach (targeted hygiene) provides a framework for maximising protection against pathogen exposure while allowing spread of essential microbes between family members. To build on these findings, we must change public, public health and professional perceptions about the microbiome and about hygiene. We need to restore public understanding of hygiene as a means to prevent infectious disease.
authors.affiliation: London School of Hygiene & Tropical Medicine and International Scientific Forum on Home Hygiene, The Old Dairy Cottage, Montacute, Somerset TA15 6XL, UK sallyfbloomfield@aol.com.
authors.forename: Sally F
authors.initials: SF
authors.lastname: Bloomfield
authors.affiliation: Centre for Clinical Microbiology, Department of Infection, University College London (UCL), London, UK.
authors.forename: Graham Aw
authors.initials: GA
authors.lastname: Rook
authors.affiliation: Center for Hygiene and Health, Department of Biology, Simmons College, Boston, MA, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Scott
authors.affiliation: APC Microbiome Institute, University College Cork - National University of Ireland, Cork, Ireland.
authors.forename: Fergus
authors.initials: F
authors.lastname: Shanahan
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Stanwell-Smith
authors.affiliation: Section of Paediatrics (Allergy & Infectious Diseases) and MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, Imperial College London, London, UK; Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, NSW, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Turner
mesh_terms: D003697:Delphi Technique; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D006920:Hygiene; D061148:Hygiene Hypothesis; D006967:Hypersensitivity; D008297:Male; D064307:Microbiota
keywords: allergy; antibiotics; cleaning; diet; hygiene; infectious disease