Why your washing machine smells…

Our lead scientist also writes the ‘Hygiene Mythbuster’ column for Cleaning Matters magazine. In this article he looks at why washing machine odours are on the increase…

Do you ever worry about germs in your gusset? Or bacteria in your budgie smugglers?

A recent study in America showed pretty much all new – yes, new – clothes are contaminated with bacteria, viruses and other stowaways such as yeasts, fungi and microscopic parasitic worms, all of which got there by other people having tried the clothes on.

Ick.

It recommended all new clothes should be washed before use, especially underwear and swimwear.

But even that might not be enough. Another study has shown even freshly-laundered ‘clean’ knickers still contained about a tenth of a gram of faecal matter. That might not sound like a lot but still represents billions of bacteria.

Low temperature laundry often is blamed for this; another study found living bacteria including Staphylococcus aureus and E. coli on 83% of laundered underwear samples, 89% of which had been washed at temperatures of 40°C or lower.

Indeed, many people have sacrificed high-temperature laundry cycles on the altar of energy efficiency and switched to detergents that recommend wash temperatures as low as 15°C, to the extent it is now reckoned the average washing machine load contains over 100 million E. coli at any one time.

No wonder complaints of washing machine odours are rising.

The problem is many of the faecal bacteria that can make us sick are remarkably resistant to heat – but that’s not all.

Washing at 30°C or 40°C kills just 6 % of house dust mites, compared with 100% at 60°C – and dust mites produce significant quantities of allergens.

Of course, we are pretty resilient when it comes to environmental geras and our immune systems constantly deal with such challenges without fuss; but what about food or health care workers laundering their uniforms at home at low temperatures? Could they pass on infections?

Many have voiced concerns that contaminated uniforms or wearing them in public may contribute to the spread of healthcare-associated infections. While that sounds entirely plausible there is no evidence this has ever caused a hospital infection.

There is also no strong evidence that health care workers wearing uniforms in public or laundering them at home has ever had any negative impact on patient safety. 

So while there are few things in life about which one can be certain, we can be sure that a washing machine that is only ever run at low temperatures will be a breeding ground for Our Microbial Overlords.

So if the stench of their plotting against you is a concern, a few hot cycles usually puts them back in their place.