Q. How can I prevent my 5-month-old son from getting sick while we travel over the holidays? I'm concerned about the germs he might be exposed to in airports and on airplanes.

A. You're wise to want to reduce the risk of your baby contracting winter viruses, especially during holiday travel time. Your baby falls within the age range -- 4 to 8 months -- in which infants are most susceptible to infections. The immunity that was transferred to him through your placenta during pregnancy begins to wear off at about 3 months of age, and his own immune system won't mature until the end of his first year. To keep him well, you must give him protection on the inside (by building up his immune system) and the outside (by reducing his exposure to germs). Try the following preventive techniques:

Boost your baby's immune system. If you are breastfeeding, continue for as long as possible. According to the American Academy of Pediatrics, if you nurse for least a year, your baby will benefit from all the immune-boosting nutrients breast milk contains. Your baby is also at the age where he is nearly ready for solid foods, so when the time comes, feed him plenty of fresh fruits and vegetables, which are filled with immune-boosting phytonutrients. Also, be sure your baby's immunizations are up-to-date according to the schedule his doctor recommends. (Your baby is probably too young to get a flu shot.)

Limit exposure to germs. A must-have item for holiday traveling is a baby sling  -- it makes the whole process easier and safer, especially in crowded places such as airports, where passersby are inclined to peer and paw at tiny babies. If a stranger comes over to coo, simply lift the edge of the sling over your baby and say, "He's about to go to sleep" (which is a bit more polite than barking, "Don't breathe on my baby!"). The baby sling also acts a deterrent to friends and relatives at holiday gatherings. They'll be less likely to invade your personal space to hold your baby.

When booking your flight, ask to be seated in a row with an empty center seat. Unless the flight is full, airlines will usually agree to this courtesy for parents traveling with infants. If you and your husband are traveling together, book an aisle and window seat for yourselves and ask that the center seat be left open for the baby. If someone sitting near you is coughing, sneezing, or otherwise seems ill, ask to be moved to another seat.

Another smart-traveling trick: Sometimes to save fuel costs, airlines will turn down the mechanisms that circulate air. If the air seems particularly stuffy, ask the flight attendant whether the circulation system is on. If not, ask that it be turned on and kept on.

Hose little noses. Most viruses enter our bodies through the nose and respiratory passages. The low humidity of a plane's cabin air can dry out the breathing passages, limiting their self-cleansing abilities. Every hour or two during the flight, spritz a few drops of saltwater into your baby's nose to flush out anything that may have accumulated. You can also use a nasal aspirator to suck out the liquefied secretions.

Insist on careful handwashing. Even though most viruses are transmitted through the air, there are many that can be transmitted by touching infected hands and toys. Insist that anyone holding your baby wash their hands first. If your baby is playing with toys that belong to a friend or relative, be sure to wipe the toys down first.

Observe the above precautions, and you and your baby will likely enjoy a healthy, happy holiday. Babies are a lot tougher than we give them credit for, so be prepared  -- not paranoid.

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