Blow your nose at your own risk
Researchers have found blowing your nose could blast infected mucus back into the sinuses, making a cold worse and perhaps leading to sinus infections.
"Nose blowing is the mechanism by which nasal fluid is propelled into the sinus," the researchers told a meeting sponsored by the American Society of Microbiology.
Dr Owen Hendley of the University of Virginia and colleagues studied 14 volunteers who had colds.
They measured the pressure in their sinuses and checked to see how much mucus was up in there.
They put a special imaging dye into the noses of their volunteers, had them blow and then did a CT (computed tomography) scan of their sinuses.
The dye appeared in the sinuses of all four volunteers who blew their noses for the tests, but none of those who simply coughed and sneezed.
Earlier studies have shown that adults who have colds blow their noses an average of 45 times a day for the first three days.
Hendley's team suggested using over-the-counter medications as early as possible in a cold to dry up the mucus.