Bacteria can include Staphylococcus aureus, which is resistant to antibiotics and can cause sepsis, pneumonia or toxic shock syndrome.
A new study now brings forward the startling revelation that hot-air hand dryers in public bathrooms 'suck in' bacteria from flushing toilets.
While previous studies have already shown that dryers can disperse germs from people's hands on to surrounding surfaces, the new findings imply less powerful versions actually bathe hands in bacteria circulating in bathrooms.
When petri dishes containing 'bacteria food' are kept in bathrooms without hand dryers, just six pathogen colonies grow within 18 hours compared to up to 254 after being blasted with such air for just 30 seconds, a study found.
These bacteria can include Staphylococcus aureus, which is resistant to the antibiotic methicillin and can cause life-threatening sepsis, pneumonia or toxic shock syndrome.
The study authors say that due to hand dryers' abilities to transmit spores, they could potentially spread Clostridium difficile, which causes watery diarrhoea that can lead to severe dehydration.
Results further suggest hand dryers can spread the bacteria Bacillus subtilis strain PS533.
The researchers add hot-air dryers' potential to transmit C.difficile should be investigated further.
Findings also imply when dryers are fitted with high efficiency particulate air filters, which remove 99.97 percent of particles larger than 0.0003mm, their bacteria counts are reduced by around four times.