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While I often use this blog to promote better hand and respiratory hygiene, I must confess to a fascination with the hygiene hypothesis.
For those unfamiliar with it, this is multi-faceted and controversial theory that proposes that some diseases common to modern man may come about due to a lack of exposure to various biological agents (bacteria, viruses, and even parasites) . . . particularly in early childhood.
Research over the past decade has increasingly linked the use of household cleaners (bleach, disinfectants, carpet cleaners, etc) and other chemicals (turpentine, insecticides, etc) to childhood onset asthma and allergies (see MedNews Today Asthma in kids linked to household cleaning products and chemicals).
Essentially, the hygienic hypothesis says we may be trying to be `too clean’ for our own good.
Back in 2010, I wrote about a University of Michigan study that addressed growing concerns over two commonly used chemicals – Triclosan and Bisphenol A (BPA) - and their possible impacts on our immune systems.
Study: Bisphenol A, Triclosan and The Hygienic Hypothesis
While my article focused mostly on BPA, Maryn McKenna took a deeper look at the use of Triclosan, and at the `hygienic hypothesis’ in her Superbug Blog entry called: Triclosan, allergies and the “hygiene hypothesis”.
Very much worth reading.
All of which serves as prelude to a new study today, from the Johns Hopkins Children’s Center, that links antibacterial chemical exposure to a higher incidence of allergies in children.
First some excerpts from the press release, followed by a link to the study, and finally a few closing comments.
Antibacterials in Personal-Care Products Linked to Allergy Risk in Children
MEDIA CONTACT: Ekaterina Pesheva
EMAIL: epeshev1@jhmi.edu
PHONE: (410) 502-9433June 18, 2012
Exposure to common antibacterial chemicals and preservatives found in soap, toothpaste, mouthwash and other personal-care products may make children more prone to a wide range of food and environmental allergies, according to new research from Johns Hopkins Children’s Center.
Results of the NIH-funded study are published online ahead of print June 18 in the Journal of Allergy and Clinical Immunology.
Using existing data from a national health survey of 860 children ages 6 to 18, Johns Hopkins researchers examined the relationship between a child’s urinary levels of antibacterials and preservatives found in many personal-hygiene products and the presence of IgE antibodies in the child’s blood. IgE antibodies are immune chemicals that rise in response to an allergen and are markedly elevated in people with allergies.
“We saw a link between level of exposure, measured by the amount of antimicrobial agents in the urine, and allergy risk, indicated by circulating antibodies to specific allergens,” said lead investigator Jessica Savage, M.D., M.H.S., an allergy and immunology fellow at Hopkins.
The researchers caution that the findings do not demonstrate that antibacterials and preservatives themselves cause the allergies, but instead suggest that these agents play a role in immune system development.
<SNIP>
Children with the highest urine levels of triclosan had nearly twice the risk of environmental allergies as children with the lowest urinary concentrations. Those with highest levels of propyl paraben in the urine had twice the risk of an environmental allergy. Food allergy risk was more than twice as pronounced in children with the highest levels of urinary triclosan as in children with the lowest triclosan levels. High paraben levels in the urine were not linked to food allergy risk.
The study, which appears in the Journal of Allergy and Clinical Immunology, is called:
Urinary levels of triclosan and parabens are associated with aeroallergen and food sensitization
Jessica H. Savage, MD, MHS, Elizabeth C. Matsui, MD, MHS, Robert A. Wood, MD, Corinne A. Keet, MD, MS
For more on the Hygiene Hypothesis, a couple more resources to consider.
First, from a Scientific American podcast from April of 2011, an interview with Johns Hopkins School of Medicine researcher Kathleen Barnes, who studies this theory.
Can It Be Bad to Be Too Clean?: The Hygiene Hypothesis
Johns Hopkins School of Medicine researcher Kathleen Barnes talks about the hygiene hypothesis, which raises the possibility that our modern sterile environment may contribute to conditions such as asthma and eczema
Another, highly controversial aspect of this theory, is that intestinal parasites (ie. worms) – which have been largely eliminated in the western world - are actually beneficial, and can help prevent (or even cure) certain types of inflammatory bowel disease.
NPR (along with many other media outlets) covered this story at length back in 2010 (see Eat Your Worms: The Upside Of Parasites).
This past week, with the release of an avalanche of News From The Human Microbiome Project, we are learning just how much of our body consists of non-human microbes – which exist in or on just about every part of the human body.
Over hundreds of thousands of years man has evolved to co-exist with – and yes, even depend upon - many of these micro organism to protect our skin, digest our food, and even produce vitamins and anti-inflammatory compounds in our intestines.
Chemicals (and drugs - see The Other Reason Not To Abuse Antibiotics) that can upset the balance of these naturally occurring – often beneficial – organisms have the potential to affect our health in unexpected ways.
While intriguing, the Hygiene Hypothesis remains both controversial and unproven.
Good hand hygiene, avoidance of infection, and general cleanliness remain essential parts of staying healthy, and no one is seriously suggesting we indulge in geophagy (eating dirt), intentionally ingest worms, or move down into the sewers to enhance our immune system.
But there is increasing evidence to suggest that our modern mania for cleanliness - particularly with the use of chemicals like triclosan and parabens – may exact an unexpected cost on our overall health.
How much of a penalty is involved, and whether the tradeoff is worth it, are questions that are yet to be answered.
