Humidifiers: How to Choose the Right One

The solution to that problem is easy. Use the cleanest water you can find; distilled water is the best. Never leave water sitting in the humidifier when you're not using it. Also, make sure to clean the unit thoroughly and regularly—at least weekly—with bleach or vinegar to kill bacteria and mold spores. And, just in case you don't get rid of every germ in the system, place the humidifier away from your child's bed, so that the mist and the germs in it don't settle directly on your child.

You also can reduce—but not ever eliminate—the likelihood that your humidifier will grow bacteria or mold by adding an antibacterial agent, or "bacteriostat," to the water. Typically, you add one capful of the solution per gallon of water in the tank. You must add the solution religiously or it won't do any good, says Bill McTighe, an indoor air-quality specialist with Home Environmental, Inc.

Dr. Sublett does not encourage parents to turn on a humidifier at all, but instead recommends good hydration from the inside. He says to make sure your child drinks plenty of fluids, especially water. He also advocates saline-based nasal drops to ease congestion. The drops, available over the counter, soften mucus, allowing it to drain or be suctioned easily with a bulb syringe.

If you feel that your child would benefit from more humid air, but don't want to use a humidifier, Dr. Loughlin suggests a simple, low-tech approach. Put a bowl of water in the room—on a radiator, if you have one. The water will evaporate into the air and increase the humidity with no electricity required.