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PRESS RELEASE
Strictly embargoed until 00.01 am, Tuesday 18 May 2004
Rising allergies are not caused by clean homes or
overdoing hygiene, says new report
A new in-depth report published today concludes there is no justification for the idea that
current standards of home cleaning and home hygiene are a factor in the rise in allergies.
The report represents the first detailed review by infectious disease and hygiene
specialists of the ‘hygiene hypothesis’ - the idea that having fewer childhood infections,
because of cleaner homes and smaller families, may be responsible for more children
developing allergies and asthma.
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The report finds that there is significant evidence that changing exposure to microbes
may indeed be a factor in the rise in allergies. But it finds no evidence that cleaning habits
prevalent today are to blame and it firmly dispels the notion that we are living in superclean, germ-free homes.
‘The hygiene hypothesis and its implications for hygiene’ compiled for the International
Scientific Forum on Home Hygiene (IFH) 2, evaluates the various medical, public health,
and environmental and lifestyle changes that might have altered our exposure to
microbes, and outlines the various other theories put forward to explain the rise in
allergies. It has been produced by public health expert Dr. Ros Stanwell-Smith3 and
Professor Sally Bloomfield4, Honorary Professor at the London School of Hygiene and
Tropical Medicine’s Hygiene Centre.
Britain is at the top of the asthma league and some estimates suggest that by 2015 half
the European population will suffer some kind of allergy, But if microbial exposure is
important, the critical changes remain elusive. A wide range of factors may have altered
patterns of exposure to microbes, including measures introduced to protect health, such
as clean water and food, sanitation, antibiotics and vaccines, as well as incidental factors
such as the move from farm to urban living.
Reducing infectious disease has been a central focus of public health policy for over a
century, but the Hygiene Hypothesis suggested there may be a price to pay in terms of
increasing allergy. The report finds little to support this worrying idea.
‘We don’t have to get infected to be protected against allergies’, says Ros Stanwell-Smith.
‘It’s looking more and more likely that exposure to the harmless microbes that live all
around us, or to harmless doses of harmful ones, is what’s important’. A study of 24000
Danish families published in the last few weeks comes to similar conclusions (British
Medical Journal, 30 April 2004).
Far from being sterile, the report also shows that most homes abound with a rich mix of
microbes - some harmless, others less so - however clean they look. ‘Our routine daily or
weekly cleaning habits actually have little effect in reducing our “background” exposure to
microbes’, says hygiene expert Professor Sally Bloomfield, ‘but what concerns me is that
while our homes may look spotless, our hygiene standards in terms of controlling harmful
microbes aren’t as good as we think’.
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At a time when more people than ever are reporting a bout of gastro-intestinal disease ,
the report warns that the popular notion that we are becoming ‘too clean’ not only has the
potential to further undermine defences against infection in the home, it may also
jeopardise attempts to improve hygiene standards in hospitals, schools and restaurants.
While strongly supporting further research into links between microbial exposure
and allergies, the report advocates renaming the ‘hygiene hypothesis’ the ‘microbial
exposure hypothesis’ which better reflects current thinking. Allergists and
immunologists are starting to say the same6. ‘We need a name that is less likely to
mislead people into feeling poor hygiene could be good for us’, says Ros Stanwell-Smith.
On the positive side, the report shows that it is entirely possible to improve hygiene
standards and defences against infection without reducing ‘background’ exposure to
microbes, should this prove to be in some way beneficial. As Sally Bloomfield explains,
‘the “targeted hygiene” approach IFH has been developing over the last seven years
argues that we should focus our hygiene effort on controlling microbes in the places and at
the times that matter, simply to prevent exposure to doses that could make us ill’. The
targeted hygiene approach is based on the same risk analysis system (HACCP) that the
Chief Medical Officer intends to introduce throughout the NHS to control hospital-acquired
infections.
For more details, or to obtain an electronic or a hard copy of the report, visit the IFH
website www.ifh-homehygiene.org
To interview either of the authors, please contact Sally Bloomfield on 07919 554781 or
John Pickup on [email protected] or 01746 787696 or on 07850 091121.
Ends.
Notes to Editors:
A pdf file of the full report will be available for downloading from www.ifh-homehygiene.org
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2
Bacteria, viruses, fungi or components of them such as bacterial endotoxin
The International Scientific Forum on Home Hygiene (IFH) is a not-for profit, nongovernmental organisation which is working to develop and promote home hygiene
practice based on sound scientific principles. For more details about IFH visit
www.ifh-homehygiene.org
3
Dr Rosalind Stanwell-Smith is an Honorary Senior Lecturer at the London School of
Hygiene and Tropical Medicine
4
Professor Sally Bloomfield is Chairman of IFH
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A recent report from the UK Food Standards Agency suggests that that food poisoning
cases have risen dramatically over the last year. In the UK Food Standards Agency
(FSA)'s fourth annual Consumer attitudes to food survey recently published, 16% of
people interviewed claimed they had experienced a bout of diarrhoea/vomiting in the past
12 months as a result of food eaten in the UK (compared with 13% in 2000 and 2002 and
12% in 2001). This is despite the FSA’s campaigns to improve standards of food hygiene.
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Professor Graham Rook of Royal Free and University College Medical School, London,
has proposed the name “Old Friends Mechanism”, while Professor Bengt Bjorksten of the
Karolinska Institutet, in Stockholm has used the term “Microbial deprivation syndrome”.