“The hygiene hypothesis” has been offered as a possible explanation for the increase in immunological diseases such as eczema and asthma now prevalent in westernised society.

This hypothesis has been around for some time now and is based on the idea that a lack of early childhood exposure to infectious agents may increase susceptibility to allergic disease by suppressing natural development of the immune system.  Since we now live in a society that is constantly sterilised by anti bacterial sprays, wipes and sanitiser gels, it is easy to comprehend the notion that this may have a negative effect on immune system development.

Large-scale epidemiological studies have already taken place and now, a new study led by the University of Bristol’s School of Veterinary Sciences has taken research in this area one step further.  The research team, led by Dr Marie Lewis, Research Associate in Infection and Immunity, compared immune system development in piglets nursed by their mothers on a farm with siblings who were brought up in an isolator unit under very hygienic conditions and fed formula milk; similar to the differing environments that human babies are raised in.

Dr Lewis commented,

“Many large-scale epidemiological studies have suggested that growing up on a farm is linked to a reduced likelihood of developing allergic disease.  However, until now, it has not been possible to demonstrate direct cause and effect: does the farm environment actively protect against allergies, or are allergy-prone families unlikely to live on farms?”

The results showed that compared to siblings reared in hygienic conditions, the farm-reared piglets had reduced overall numbers of  stimulatory immune cells which drive immune responses.  The farm-reared piglets also had significantly increased numbers of regulating immune cells responsible for pacifying immune response and limiting inflammation.  The researchers also found that the farm-reared piglets had decreased antibody responses to novel food proteins when they were weaned; a possible beneficial effect of this shift in ratio of stimulatory and regulatory immune cells.  In conclusion, the farm reared piglets, which had been exposed to a more natural environment, complete with a bit of dirt,  demonstrated a much healthier immune balance overall.

The researchers concluded that further work was needed to clarify the underlying mechanisms and may help to develop of methods of intervention during infancy to help prevent immune diseases later in life.

Whatever the underlying mechanisms, research continues to mount against bringing children up in an overly sterile environment where each and every surface has been smothered in anti bacterial spray and every single step forward is accompanied by a packet of wipes.


Is it fair to conclude that a little dirt never did hurt and perhaps a life without any at all is more of a worry?  You decide…



Direct experimental evidence that early-life farm environment influences regulation of immune responses, Marie C. Lewis, Charlotte F. Inman, Dilip Patel, Bettina Schmidt, Imke Mulder, Bevis Miller, Bhupinder P. Gill, John Pluske, Denise Kelly, Christopher R. Stokes & Michael Bailey, Pediatric Allergy and Immunology, published online ahead of print 03 February 2012.

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