Humidifiers are commonly used to increase indoor humidity, or the level of water vapor in the air. These devices are typically used in the winter months, since indoor heating systems and cold temperatures lead to low humidity levels. Countering this dry air helps reduce dryness in the skin, eyes and nasal passages, and may even be linked to a reduced risk of colds and the flu. Optimal humidity can also protect your home furnishings. However, high levels of humidity and improper use and care of humidifiers can pose health risks.
Humidifiers can reduce skin and lip dryness during the winter months. Optimal humidity can also prevent dryness in the mouth and nasal passages, improving comfort during sleep and potentially reducing cough and cold symptoms. While optimal humidity isn’t universally defined, the U.S. Environmental Protection Agency (EPA) recommends keeping the relative humidity -- a measure of the amount of vapor in the air compared to how much vapor the air could hold at a certain temperature -- between 30 to 50 percent. Levels can be monitored with a device called a hygrometer, which is built into some humidifiers.
Cold and Flu Protection
Preliminary evidence suggests optimal humidity reduces the risk of influenza and upper respiratory infections, although data specific to the use of humidifiers on these illnesses is lacking. An article published in the March 2009 issue of “Respiratory Medicine” linked both a drop in outdoor temperature and humidity to an increased occurrence of upper respiratory infections, the common cold and sore throats. In addition, an animal study determined that low air humidity enhanced transmission of the influenza virus, according to a report in the October 2007 article in “PLoS Pathogens.” More research is needed to study the role of humidifiers in reducing infection risk.
Asthma and Allergies
Children and adults with asthma may find humidifiers improve comfort by keeping nasal passages and airways from drying out. A humidifier may be more likely to ease symptoms when asthma is compounded by an upper respiratory infection. However, limited research supports the benefits of humidifier use in people with asthma. In addition, if the humidifier puts too much moisture in the air, it can worsen asthma, since mold and dust mites -- known asthma triggers -- thrive in a humid environment. So if you plan to use a humidifier in the home, take steps to ensure the humidity stays below 40 or 50 percent, according to the American Academy of Allergy, Asthma and Immunology.
Besides health benefits, humidifiers may help your home -- particularly if you live in dry climates or experience cold winter months. Humidifiers reduce dryness so there is less static electricity in the air. In addition, a humidifier can protect wood floors, artwork, wood furniture, paint and wallpaper by preventing exposure to excessively dry air. However, high humidity can promote the growth of mold and cause damage to furnishings.
To minimize risks and optimize benefits, it is important to properly care for your humidifier. Read the manufacturer’s instructions for use and cleaning of your unit. Change the filter regularly to prevent mold growth. The EPA recommends that distilled or demineralized water be used in cool-mist humidifiers, which are more likely than warm-mist units to expel minerals and microorganisms from the water into the air. These cool-mist units can send a white dust into the air, which can be irritating to some, and at least one case report linked humidifier white dust to lung injury in a child, according to a February 2011 article in “Pediatrics.” If you or your child has asthma, seek medical advice before using a humidifier in your home.
Reviewed by Kay Peck, MPH RD