Germs In the Mist
Adding to the confusion is the fact that, while each type of humidifier has its benefits, there are health risks associated with them. Any wet environment can harbor germs and cause mold to grow—and a humidifier is, by definition, wet.
With humidity, too much of a good thing is bad. "Humidity levels above 50 percent set up an environment ideal for the growth of mold and dust mites," says Dr. James L. Sublett, MD, FAAAI, managing partner of Family Allergy & Asthma, a group of asthma and allergy specialists in Kentucky and Indiana.
If you see condensation forming on the windows, lower the humidity level. If you see mold or mildew starting to form around the windows, on the walls, or anywhere else in your child's room, turn off the humidifier immediately. The mold can be much more dangerous than the stuffy nose you're trying to alleviate.
The drawback of a cool-mist unit is that the water isn't boiled and is more prone to breeding mold spores and bacteria, and spreading them throughout the room. Those particles can lead to further coughing as well as allergic reactions such as wheezing and skin problems.
However, warm-mist humidifiers, despite the boiled water that they use, are not germ free. "There are no germ-free vaporizers," says Dr. Sublett. "Even in a hospital setting, it is impossible to sterilize a humidifying device." Warm-mist humidifiers and vaporizers pose not only potential health risks, but also a safety hazard. The boiled water is very hot, as is the mist or steam that comes out of the unit. If you use a warm-mist unit, make sure that it is safely out of your child's reach.