Hot water or cold? Soap or handwash? Towels or hot air dryers? The post-bathroom ritual is a vital task – but is there a best way to do it?
Now wash your hands! It sounds straightforward, but it isn’t. Although there’s plenty of evidence that washing your hands after you’ve been to the loo, before eating, or after travelling on public transport can reduce the spread of disease, only 5% of people wash their hands properly all the time.
An observational study of more than 3,000 people found 10% left public toilets without washing them at all and even if they did, 33% didn’t use soap. This matters because, unfortunately, we can’t resist touching our faces, allowing germs to spread nicely from our hands to our noses and mouths, where they can get into the body. Researchers in Brazil and the US found that we touch surfaces in public spaces an average of 3.3 times an hour and we touch our mouths or noses about 3.6 times an hour.
So it’s clear that we need to wash our hands properly. The problem is there are plenty of myths out there about how to do it.
?Does the water need to be hot to get your hands clean
In a survey of 500 adults in the US, 69% believed that the temperature of the water has an impact on the effectiveness of handwashing. It is true that heat can kill bacteria (which is why we need to make sure certain foods are piping hot when we eat them), but the water would need to be scalding for this to happen on your skin. Salmonella, for example, can survive temperatures of 55C for more than 10 minutes. If you washed your hands in water this hot you would have serious burns before 30 seconds were up.
To find out exactly how many microbes remain on our hands after washing in water ranging in temperature from 4.4C to 50C (39.9F to 122F), researchers in Florida used a method known as the glove-juice technique (though it’s not a juice you’d want to drink). Volunteers’ hands were wiped with a bacterial soup or with raw minced beef. Then their hands were washed in water of a certain temperature before they put on latex gloves and a special solution was poured into the gloves. After a minute of hand massage through the glove to make sure all those bacteria got into the liquid, the glove juice was collected using a pipette, ready for testing in the lab. They found that whether the water was cold, hot or middling made no statistically significant difference to the quantity of bacteria remaining on people’s hands.