During cold and flu season, we're inundated with messages to wash our hands frequently.
But to avoid getting sick, it's also important that we stop touching our noses and mouths all the time, a new study shows.
Every time people touch their mouth or nose, they transfer bacteria and viruses between their face and their hand.
This "self-inoculation," or transfer of germs from one body part to another, is a primary way that germs wind up spreading from contaminated surfaces to people's faces, and from sick people to often-touched surfaces.
"There are many opportunities in between hand-washing episodes for people to re-contaminate their hands," said study researcher Dr. Wladimir Alonso, a global health researcher at the National Institutes of Health in Bethesda, Md.
Alonso and colleagues randomly selected 249 people in public places, on the Washington, D.C. subway and in the Brazilian city of Florianopolis.
The researchers observed them, noting how often they touched a common surface and then their mouth or nose. They found that people touched their faces an average of 3.6 times per hour, and common objects an average of 3.3 times per hour.
This rate of self-touching means that people likely get germs on their hands much more frequently than they wash germs off their hands, according to the study.
"It is important to understand the basic mechanisms through which diseases are transmitted to take full advantage," of hand-washing, Alonso said.
Recommendations issued to the public typically emphasize hand-washing, but during potentially severe disease outbreaks, the messages should be shifted to ensure that people understand how self-inoculation occurs, and avoid touching their faces, the researchers said in their study.
"If a deadly respiratory virus is around, this is something to really take into account," Alonso said, pointing to the 2009 flu pandemic as one example of a situation where knowledge of self-inoculation could limit the spread of disease.
Alonso said that knowing how often self-inoculation happens should not turn people into hypochondriacs, or toward a life of discomfort and constant state of alert. The immune system offers good protection against diseases.
"But it is also important to be aware that re-contamination can occur very quickly after we wash our hands," he said.
The findings were published Nov. 15 in the journal Clinical Infectious Diseases.
Pass it on: Touching your mouth or nose can spread the flu.