Woman's hand holding humidity therometer in a child's bedroom

Dry air makes fighting a cold or sinus infection harder. When your throat itches and your eyes feel raw, would adding moisture to the air with a humidifier help?

High humidity levels promote the growth of mold and dust mites – two common allergens associated with allergy and asthma symptoms – and without careful maintenance, humidifiers can be dangerous breeding grounds for bacteria.

How do you find the right balance between comfort and protection for your health?

First, assess your need. A humidity gauge called a hygrometer can help you decide. Inexpensive and available at most home supply stores, a humidity gauge can measure humidity levels in every area of your home. Chances are, levels will be different in each room.

Humidity levels inside your home will probably vary from day to day, depending on the overall climate, how cold it is outside, how much outdoor air comes into your home, and how much moisture is generated inside from cooking, bathing and general everyday life.

The U.S. Centers for Disease Control and Prevention (CDC) and Environmental Protection Agency (EPA) both recommend keeping humidity levels between 40 and 50 percent.

Making the right choice

When treating a cold or other respiratory infection, you may want to run a humidifier in a bedroom at night. However, since most of us spend so much time in our bedrooms – the primary breeding grounds for dust mites – humidity control there is particularly important.

Use a humidity gauge and limit the time the humidifier is run if levels begin to rise. Measure the square footage of the room to make sure you choose the right size unit.

To keep humidity levels stable throughout your home, consider installing a humidifier unit into your HVAC system. When tied into your water line, it requires no refilling and poses no danger of bacteria growing in standing water. (Follow manufacturer’s instructions for periodic cleaning.) Central units are usually less expensive to run, but require professional installation.

Types of humidifiers:

Evaporator – uses a fan to draw air over a very large wet wick, filter or belt, producing a mist. Usually inexpensive, but fan can be noisy; unit needs frequent refills and standing water can grow germs.

Steam vaporizer – actually boils the water, releasing steam into the room. The boiling kills bacteria, but steam and hot water are dangerous around children and pets.

Impeller or “air washer” – uses rotating discs to break the water into a cool mist. The disc technology also captures some dust and other impurities in the air.

Ultrasonic – uses high-frequency vibrations to break water into a cool mist. These units are quieter than those with fans and can quickly produce a lot of moisture. Many have added features that reduce mineralization of water and bacteria growth, but replacement cartridges can be expensive.

Keep It Clean

Control bacteria produced by humidifiers by taking the following precautions:

  • Aim humidifier mist away from carpets, drapes and other furnishings, to prevent moisture accumulation.
  • Use distilled or demineralized water, as tap water contains minerals that can create deposits (seen as white dust) that promote bacteria.
  • Empty unit, dry inside and refill with clean water daily.
  • Clean unit with a hydrogen peroxide or white vinegar solution at least once a week. Avoid using bleach, which can irritate lungs. Rinse tank after cleaning.
  • Change filters at least as often as the manufacturer recommends.
  • Drain, dry and clean humidifiers before storing them; clean them again when you take them out for use.

Reviewed by Peyton Eggleston, MD