While we might hope bathroom hand dryers are helping to clean and dry our hands, a new study has suggested that they are in fact covering them in poo.
The University of Connecticut carried out a study to identify whether the dryers were helping to disperse germs, or just redistributing them.
The paper, published in the Applied and Environmental Microbiology, found that dryers spread germs.
The unhygienic process begins when you flush the toilet with the lid open.
This sends faecal particles into the air, where they linger until you turn on the hand dryer.
The particles are then heated up in the machine and spat back out over your wet hands, which is a particularly healthy environment for germs to thrive in.
This also means that if your toilet is in your bathroom and your toothbrush is exposed, there is probably faecal particles on that too.
These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers and that spores could be dispersed throughout buildings and deposited on hands by hand dryers, the study concluded.
Researchers suggest fitting dryers with HEPA (high efficiency particulate air) filters, which can reduce the bacterial deposition by four times.
Alternatively paper towels are found to be more hygienic, but that option is also less environmentally friendly and potentially more costly.
The consequence of hand dryers spreading poo is unlikely to have a serious effect on your health, however, as many day-to-day items, such as mugs and desks, are also covered in germs.