The hygiene mythbuster

02 July 2014

Seán Derrig, scientific director at Chemex International, asks the question 'Are we too clean?'

You may have come across the Hygiene Hypothesis – the idea that asthma and allergies are on the increase (especially in our kids) because we keep everything just too clean nowadays. If we exposed them to more dirt, got rid of antibacterial cleaning products and our obsession with hygiene everyone would be far healthier.

Luckily for our industry the tiny kernel of biological plausibility behind this myth is obscured by many misconceptions and half-truths. ‘Cleanliness’ and ‘hygiene’ are not the same but are often confused; there’s a huge difference between children getting dirty when they interact with each other or their environment and not washing hands after visiting the lavatory, before eating food or after farm visits. This was demonstrated again last month with another petting farm-related E. coli outbreak.

It’s true that mass vaccination plus improvements in sanitation, diet and lifestyle have transformed life expectancy and diminished the risks posed by what were ‘killer’ bugs a generation ago. And if we’re unlucky there are still antibiotics that work. Just.

Many forget we are constantly exposed to millions of innocuous microorganisms of one flavour or another and we don’t even notice; our body recognises any marauders and the immune system sorts them out. Add to that our ‘normal flora’ (the billions of microorganisms we carry on and in us) and you quickly realise we are not alone; we might be born germ-free but it only takes 48 hours or so to pick up our own ‘fingerprint’ of similar but slightly different bacterial species we then carry for life.

Were ‘too much cleanliness’ causing asthma in children, for example, we’d expect to see it across all backgrounds rather than disproportionately in impoverished inner cities or where pollution levels tend to be higher. And don’t forget genetics, diet, stress and multiple other influences all affect susceptibility. It’s complicated. Also you just need to look at any hand washing survey and you’ll realise most people aren’t ‘too clean’ – quite the opposite.

The key purpose of good hygiene is to reduce exposure to harmful germs but effective cleaning is only part of that. As an industry we need to foster understanding of how potentially harmful bugs are transmitted, what hygiene interventions are appropriate and when to deploy them.

Staff misconceptions when cleaning critical environments can have serious consequences. A recent hospital study used invisible UV markers to assess cleaning diligence: in normal rooms up to 90% of the markers were removed but those cleaning isolation rooms removed 20% or fewer. This was because staff did not understand the tiny relative risk posed to them by a patient with MRSA or C. diff.

So, ultimately it doesn’t really matter how much we clean – without an understanding of the basics of hygiene infections will continue to be spread unnecessarily.