Blowing your nose to alleviate stuffiness may be second nature, but some people argue it does no good, reversing the flow of mucus into the sinuses and slowing the drainage.

To test the notion, Dr. J. Owen Hendley and other pediatric infectious disease researchers at the University of Virginia conducted CT scans and other measurements as subjects coughed, sneezed and blew their noses. In some cases, the subjects had an opaque dye dripped into their rear nasal cavities.

Coughing and sneezing generated little if any pressure in the nasal cavities. But nose blowing generated enormous pressure — “equivalent to a person’s diastolic blood pressure reading,” Dr. Hendley said — and propelled mucus into the sinuses every time. Dr. Hendley said it was unclear whether this was harmful, but added that during sickness it could shoot viruses or bacteria into the sinuses, and possibly cause further infection.