Humidify? Dehumidify?

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Sometimes you read that you need a humidifier for your health, then you turn around and read that you need a dehumidifier to prevent the growth of mold, mildew and dust mites. This can be confusing. Before you buy either, find out if there is a problem. You can accurately measure humidity (water content of the air) with a digital humidity gauge. They are widely available and cost ~$20. Many also display the high and low humidity for the past 24 hours. The goal is to keep the humidity between 35 and 50%. Consider a dehumidier if the humidity is above 50%. Dust mites can't drink water; they have to absorb it from the air. Dust mites and mold grow better in higher humidity. High humidity also makes the air feel damp, which can worsen asthma and allergies. Consider a humidifier if the humidity is below 35%. Low humidity, more common in winter months, can cause dry, itchy skin, nosebleeds, sinus headaches and, like high humidity, flare asthma and allergies.

If you get a humidifier, rule #1 is Keep It Clean. They cause more problems than they solve if you start spewing bacteria and mold up into the air. Warm mist humidifiers are easier to keep clean than cool mist humidifiers, but the warm air may burn a child, so be careful. We tell patients that when they are infected, temporary use of a humidifier can reduce coughing and congestion and loosen the mucus. From April to October, your air conditioner probably takes adequate humidity out of the air, so you may only need to use a dehumidifier during Houston's winters.

David B. Engler, MD

Note: Information contained in this article should not be considered a substitute for consultation with a board-certified allergist to address individual medical needs.