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Why Home Humidity Control Matters

Contest Winner Happy New Year and Welcome to the January edition of the National Allergy Educational E-Mail Newsletter! This month we will discuss Why Home Humidity Control Matters. If the relative humidity in your home is too high or too low, you could be suffering with allergies or sinus problems unnecessarily. Even if you live in a region with drier winter months, indoor air can be full of dust mites and mold spores. This is an important concern because we spend so much more time indoors during the winter. Read on to discover a strategy for keeping dust mite and mold allergen under control this year.

In This Month's Issue:
National Allergy January CouponIf you're new to the newsletter or you'd like to reread any of our newsletters, you can find all of our past issues on our website. In the coming months we'll have more educational articles about the aggravating factors behind allergy, asthma, and sinus problems as well as helpful tips and valuable subscriber-only coupons. To top it off, we're giving away an Austin Air HM-400 Air Purifier, valued at $449.99, to one lucky subscriber every month! Click here for a list of previous winners.


Katie Weaver & The National Allergy Newsletter Team


Why Home Humidity Control Matters

Is It A Winter Cold Or Allergies?

Is It A Winter Cold Or Allergies?This is a tough question to answer in a few sentences and without taking a good look at your symptoms and their frequency. However, there could be more to your winter sniffles than simple cough and cold season. I have a friend who seems to have chronic colds that last for months. She went to her parent's home in the mountains for the holidays and felt much better. It could be that home cooking and time with family improved her symptoms, or that she is allergic to something that is in her own home. Two common home allergens that are year-round problems are dust mite and mold spore, both of which can be controlled in a variety of ways.

If you suspect that your sniffles and congestion have lasted too long to be a simple cold or your mucus is running clear, you might consider visiting an allergist to see if mold, dust mites or other allergens may be causing your symptoms.

Dust Mite Control

Americans spend many more hours indoors during the chillier, often wet, winter months than during other seasons. The more time we spend in areas like our bedroom or living room, the more food we are providing for dust mites - remember, they feed on our dead skin cells and other organic matter. And, the reason most of us enjoy being inside so much in the winter is that it is nice and warm. Sounds like a recipe for indoor allergens.

One way to control the mite population is by lowering relative humidity. Countless studies have shown the link between humidity and the prevalence of dust mite populations. The reason is simple: 70-75% of the weight of a house dust mite is water. They maintain this needed water level through the absorption of water vapor in the air. So high relative humidity is crucial to their survival. Some of the leading experts in the field of dust mites and their allergen wrote the following:

"Maintaining RH [relative humidity] below 50% is one of the most common recommendations for reducing dust mites and their allergen levels in homes because ambient RH is the key factor that influences dust mite prevalence. Mites must obtain sufficient water from the air to survive. Laboratory studies have shown that adult mites die of dehydration in 5 to 11 days, depending on temperature (77° F - 93° F), when continuously exposed to RHs of 40% or 50%"
Larry G. Arlian, PhD, Thomas A. E. Platts-Mills, MD, PhD. "The biology of dust mites and the remediation of mite allergens in allergic disease." Journal of Allergy and Clinical Immunology. March 2001.

Read more from our learning library on controlling house dust mites.

Mold Control

Moisture in your home's air not only makes the environment more hospitable to dust mites, but to mold growth as well. Molds thrive in humidity at or above 50-55%. A musty smell in your basement or bathroom is likely a mold or mildew problem as a result of excess moisture - from leaks or spills or from consistently high relative humidity. Even in wintertime, when outside air does not hold as much moisture, the home is not immune from condensation (like sweaty windows) and leaks. Extra care should be taken to monitor your home's relative humidity throughout the year, especially if your region is prone to heat and moisture.

To battle the dry conditions of winter, some people use humidifiers as a way to bring moisture into the air. For many who suffer from colds or have asthma induced by dry conditions, a humidifier can mean a better night's sleep. However, humidifiers can present a mold hazard if improperly used or cared for. First, invest in a germ-free humidifier that discourages the growth of mold and bacteria. Also, be sure to regularly clean your machine, keep surrounding areas from gathering moisture, and monitor the humidity level where the humidifier is being used with an accurate gauge.

To read more about mold allergen, see our learning library feature on mold and indoor air quality.

What Is Relative Humidity?

We know that relative humidity in our home should be between 45-50%, but what exactly is relative humidity? It is the measure of the amount of water in the air compared with the amount of water the air can hold at a specific temperature. For example, a 77ø F room with 60% relative humidity means that the air is holding 60% of the total amount of water vapor it could possibly hold at that temperature. The higher the temperature, the more moisture the air can hold. So a reading of 60% humidity at 77ø F is more severe than that same reading at 50ø F. Outdoor relative humidity levels can soar during the summer months, but even in winter, when outdoor humidity levels are lower, home humidity levels are not always in the "humidity safe zone" so it is important to monitor all year round. An instrument called a hygrometer (or humidity gauge) is used to measure relative humidity in the home and is an important tool for keeping tabs on your home's humidity levels. We offer the Acu-Rite Humidity Gauge, which gives relative indoor humidity readings as well as indoor/outdoor temperature readings and time of day - all at the same time!

How Can I Control Home Humidity?

Air conditioning and electric dehumidifiers are the most effective ways to keep indoor humidity at a healthy level. Air conditioning works because cool air cannot hold as much moisture as warm air. Most dehumidifiers use this principle by using a fan or a blower to pull air in, where it then passes through a cooling coil and is chilled to its dew point. This process results in condensation on the coils, which then flows into a bucket. Some dehumidifiers allow for the collected water to be pumped through a hose and into a sink, bathtub or out a window. After passing through the coils, the moisture-reduced air is then heated back to room temperature and released into the room.

It is important to note that even dehumidifiers can harbor mold in the coils and tank if not properly cleaned. I recommend using Goodmorning Purifying Spray on coils as part of a regular maintenance routine for your dehumidifier.

Questions To Ask When Looking For A Dehumidifier

There are several key questions you should ask when looking at the various models and options for home dehumidification:

Questions to ask when buying a dehumidifier.

For basements and small rooms, we like the Whirlpool Gold Dehumidifier. We stock it in two sizes that can operate in temperatures as low as 44ø F without icing up. To experience maximum moisture-removal capability, you may be interested in a whole-house dehumidification system. Santa Fe dehumidifiers are some of the most powerful residential dehumidifiers available today. The Santa Fe is ideal for basements, and can lower the humidity in an entire home. The cabinet design on the Santa Fe Rx helps it to blend in to your home's decor while offering high-volume dehumidification. Plus, the Rx model can be equipped with an optional HEPA filter that can be operated independent of dehumidification.

Other Mold and Humidity Control Tips

  1. Monitor and regulate relative humidity levels in your home. Humidity levels should be kept around 50%. Do keep in mind, that extremely low humidity can aggravate asthma and cause skin dryness, so lower is not necessarily better.
  2. Provide adequate ventilation and air circulation in the home by installing exhaust fans and opening room doors and windows (individuals allergic to pollen or sensitive to other outdoor pollutants should use discretion about keeping windows open).
  3. Keep a close eye on areas prone to condensation. Cover cold surfaces with insulation and increase the air temperature when condensation begins to appear. Excessive condensation means that the relative humidity may need to be lowered inside.
  4. In the bathroom, run the vent fan or open windows during and after a shower so that the moisture can dissipate. Also be aware that carpeted surfaces will absorb moisture.
  5. Use a mold resistant shower curtain or one that can be easily laundered.
  6. Through daily living, adults lose 2-3 pints of water per day (not including bathroom trips). This means that upholstered furniture and bedding can also be prone to moisture and mold growth. Our BedCare Classic mattress covers are a good precaution against mold growth and they keep away the dust mites, too!
  7. Keep a limited number of houseplants, and try adding a mold-preventative to the soil.
  8. Vent your clothes dryer to the outside of the house and do not let clothes sit for long in damp heaps, in or out of the washer.
  9. Periodically check carpet laid directly on concrete surfaces as the carpeting can absorb moisture. Consider covering concrete floors or crawl-space floors with plastic sheets or tarps in moisture-prone areas.
I hope you and your family are in good health during this winter's cough and cold season. And remember, if your symptoms are lingering for more than a few weeks, you may be having allergic reactions and should see an allergist. For those of who know you have dust mite or mold sensitivities, try to keep indoor allergen levels under control, and make monitoring your home's humidity a habit in the coming year. Dust mites may not thank you but your family will!

This information is for educational purposes only. Always consult with your doctor first about your specific condition, treatment options and other health concerns you may have.

Remember that our customer service representatives have plenty of experience guiding people through the options for allergy, asthma and sinus relief, so feel free to contact us by calling one of our phone experts at 1-800-522-1448 Monday through Friday between the hours of 9:00 am and 5:30 pm Eastern Time. You can also e-mail us at


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