Both jet and warm air hand dryers spread bacteria into the air and onto users and those nearby.
Airborne germ counts were 27 times higher around jet air dryers compared to the air around paper towel dispensers, said the scientists.
"Next time you dry your hands in a public toilet using an electric hand dryer, you may be spreading bacteria without knowing it. You may also be splattered with 'bugs' from other people's hands," said Mark Wilcox, professor at the University of Leeds.
For the study, the team contaminated hands with a harmless type of bacteria called Lactobacillus, which is not normally found in public bathrooms.
This was done to mimic hands that have been poorly washed.
Subsequent detection of Lactobacilli in the air proved that it must have come from the hands during drying.
Bacterial air counts around jet air dryers were 4.5 times higher than around warm air dryers and 27 times higher compared to air around paper towels.
Lactobacilli were detected in the air 15 minutes after hand drying, found the study.
"These findings are important for understanding the ways in which bacteria spread, with the potential to transmit illness and disease," Wilcox said.
The findings were published in the Journal of Hospital Infection.
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