If you are suffering from a cold, do not blow your nose. Every time you do that, you prolong your suffering, say Jack Gwaltney and Birgit Winther of the University of Virgina in Charlottsville, USA, who studied computerised tomography (CT) scans of sinuses of patients suffering with a cold. They found that the viscous fluid in the sinuses, found in 85 per cent of people with a cold, was filled with bubbles. This was unusual as the mucous is very viscous and the bubbles could not have been created inside the sinuses. But air could have mixed rapidly with the mucous when it entered the sinuses under high pressure. The researchers inserted thin straw-like gauges up one of the nostrils of four patients. They made the volunteers sneeze, cough or blow their noses. Each blow resulted in a rapid rise in pressure. In one second, the pressure shot up to twice what is normal, which is enough to propel one millimetre of mucous into the sinuses. Sneezing or coughing, on the other hand, produced only one-tenth of the pressure of a nose blow, which is not enough to move the mucous ( New Scientist , Vol 164, No 2207).