Tha’s gorra eat a peck o’ muck afore tha dies.

For those readers not lucky enough to have been born in Yorkshire, northern England, an approximate translation of this old expression is “You will eat a barrel-full of dirt during your lifetime”.

What brought that on? According to Abby Alford, writing in the Western Mail (1), there may have been some scientific basis to the saying. Bangor University lecturer, Dr Prysor Williams, believes that an obsession with cleanliness reduces contact with dirt and thus with harmful bacteria. Our immune systems become weakened, leaving us susceptible to infection. Unfortunately, the evidence for this view is somewhat lacking, though Dr. Williams is not the only one to have argued this.

Stuart Levy, Director of the Center of Adaptation Genetics and Drug Resistance at Tufts University, provided substantial evidence that the substitution of anti-bacterial agents for good old soap and water increases the ability of bacteria to develop resistance. A few bacterial cells containing genes that confer resistance to the antibiotics can protect neighbouring sensitive cells, rendering the antibacterial agent ineffective. Levy’s group tested the ability of Escherichia coli to mutate to become resistant to triclosan, which inhibits an enzyme involved in fatty acid biosynthesis and thus interferes with membrane biosynthesis. The work was published in the prestigious journal Nature.

In a carefully constructed randomized, double-blind trial, Elaine Larson and her co-workers have also shown that using antibacterial home cleaning and hand-washing products has no significant effect on the incidence of infectious disease symptoms (2).

The take-home message is that while cleanliness may be next to godliness, we do not live in a sterile environment. If we try too hard to protect ourselves and our children from microorganisms, we don’t give our immune systems the chance to develop resistance to bacterial pathogens.

(1) http://www.walesonline.co.uk/news/wales-news/2009/02/16/
how-obsession-with-cleanliness-could-be-making-us-ill-91466-22935582/

(2) Annals of Internal Medicine, 2 March 2004, Volume 140 • Number 5 321