When you have a heavy cold, your nose runs all day but stops as soon as you fall asleep at night. What mechanism turns off the flow of mucus? Could a drug be developed to do the same and therefore alleviate the worst effect of the cold? And could such a drug also help to reduce the spread of colds?
鈥� This phenomenon is merely a matter of gravity. When you settle down to go to sleep, the action of lying on your back means that the mucus being secreted in your nasal passages, rather than running down and out of your nose, instead travels towards the back of the throat where you swallow it unconsciously.
If you sleep on your side, just one nostril (the lower one) becomes blocked, and if you want to unblock your nose, it is usually sufficient merely to alter your orientation, so if lying down, stand up, and if standing up, lie down. This reverses the direction of the mucus flow and clears the blockage.
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Alexandra McKenzie Johnston, Thirsk, North Yorkshire, UK
鈥� The runny nose that occurs while we鈥檙e awake is caused by head position. When we sleep, almost all the post-nasal drip drains down the throat because we are lying down, sometimes on our sides and sometimes on our backs. I suffer from this problem and, after testing my theory using a massage table that had a face-hole opening, I started using pillows to position my head so my nose points downhill.
Test it yourself using pillows, leaving a gap so that you can rest your head face down while leaving a space for your mouth and nose. Oh, and have some handkerchiefs ready: you鈥檒l probably find that your nose runs copiously all night.
Hank Roberts, Berkeley, California, US
鈥� The questioner is mistaken in his belief that the runny discharge is contagious. Most colds are contagious from two to four days after exposure to the virus, which is usually before the symptoms appear. Once you start to suffer from a runny nose, the infection is well under control and the amount of virus present in the nasal secretion has diminished.
The most common way to catch a cold is through hand contact with the virus rather than from people with runny noses. Colds are more easily transmitted via a hard surface that other people have touched, such as a doorknob or computer mouse.
Instead of avoiding people with runny noses, it is far more important to make sure that you do not touch your eyes, nose or mouth with your hands after they have been in contact with various objects in either your home or your office.
鈥淥nce you start to suffer from a runny nose the infection is well under control and the amount of virus present in the nasal secretion has diminished鈥�
David Gibson, Leeds, West Yorkshire, UK