Why do babies always seem to have a runny nose?

Contagious kids

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Why do babies always seem to have a runny nose?

Asked by Michael Woodhams of Palmerston North, New Zealand

There are at least three reasons why infants and young children always seem to have a runny nose. First, in fact they have more colds. Infants and young children have many upper respiratory tract infections due to a lack of a more mature immune system.

This is why children often get so many colds when they start school. Close contact for the first time with other humans (and often infectious children at that!) exposes them to many viruses they have never encountered before.

In the obverse, this is also why the elderly rarely have colds. Exposure to more viruses builds up immunity. Old people have had the exposure, young people have not.

Second, infants and young children may not always keep as warm or as cool as they should. Thus, they may be more susceptible to vasometer rhinitis. This occurs when there is a change in temperature that causes swelling in the tiny blood vessels in the mucus membrane linings of the nose and produces a runny nose.

Third, an infant or young child may not have fully developed sinuses that could cause the nose to run more often.

According to Dr Vincent Iannelli, author of The Everything Father's First Year Book (Adams Media, 2005), a baby's sinuses are not well developed. However, it is a myth that a baby has no sinuses at all. In fact, newborns have very small maxillary and ethmoid sinuses. The maxillaries are under the cheeks while the ethmoids are higher up in the nasal cavity. They are so small that they cannot be seen in a normal x-ray until the child is one to two years old.

Dr Iannelli points out that "the frontal sinuses and the sphenoid sinuses don't begin to develop until a child's second year and can't be seen on an x-ray until the child is five to six years old. The sinuses continue to grow until your child is a teenager."

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

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