Will a Dehumidifier Help with Dust Mites?

Dust mites can make your home quite uncomfortable, as they are the most common cause of dust allergies. Unfortunately, dust mites may be present without your knowledge, as they are too small to be seen without a microscope. They thrive in areas that are humid and warm, especially, in soft areas, such as carpeting, sofas, or mattresses. If dust mites are living in your home, you may experience symptoms such as sneezing, wheezing, or even the development of asthma in children.

Interestingly, dust mites don’t need liquid water to drink but rather remove water from the air for hydration. Because of this, dust mites can only survive in spaces with high relative humidity. The required humidity level will vary based on temperature, but it ranges from 55%-73%. If the humidity drops too low, dust mites will dehydrate and eventually die. Being exposed to moist air, even if it is for a short time, will extend the life of a mite. In a lab setting, mites were shown to die in 5-11 days after living in condition of 40%RH, and a temperature ranging from 25-34°C.

Currently, there aren’t many options to get rid of dust mites besides using chemicals. A research study from Wright State University, examined whether maintaining a lower humidity with the use of a dehumidifier, would prevent dust mite issues from arising. The study took place between May 1998 and October 1999 in Dayton, Ohio. Prior to beginning the experiment, there was a 1-3 week baseline screening to gauge dust mite density in the 71 selected homes.

The participants were split into three groups. Group 1 was instructed to keep the relative humidity in the their home below 51%, with the use of a 100 pint per day dehumidifier and air conditioning. Group 2 used air conditioning only, and thus, did not keep the humidity below 51%. Both Group 1 and Group 2 were instructed to keep their windows closed to prevent outside air flow. For Group 3, the only climate control was opening the windows, allowing the relative humidity to go above 51%. All three groups were instructed to maintain normal house cleaning.

Regardless of the group, every home was given two monitors to record the temperature and relative humidity on a regular basis. In each home, the first monitor was placed on the floor where the highest dust mite concentration was discovered. The second monitor was placed in the same room but on a higher surface, such as a table. In addition, two of the homes had monitors placed outside to gather outdoor conditions.

In addition to the monitors, dust sampling was completed using a portable vacuum cleaner. Dust sampling was done at the beginning of the study, and at consistent intervals during the study. The sampling was done at 3 locations- an upholstered piece of furniture in the living room, the floor next to the furniture, and the bedroom floor next to the bed.

During the testing period, the temperature during the summer ranged from 20.5°C to 25.9°C with the average outdoor RH between 64.8% and 73.3%. In the low RH group, the average relative humidity was approximately 45%, while the other homes stayed between the outdoor RH level and 45%.

The results from the study showed that maintaining a low humidity level does indeed help with dust mites. From the beginning of the study to end, the concentration of dust mites in the low RH group (Group 1) steadily decreased. In terms of numbers, the homes started out at 401.2 mites/g, which declined to 8.2 mites/g at the conclusion of the study. By comparison, the other two groups experienced an increased concentration of dust mites during the humid, summer months.

The number of dust mites paralleled the allergen levels, meaning Group 1 had considerably less allergens present than the other groups. After 17 months, the number of allergens for the low RH group was 10 times lower than the other homes.

It can be concluded that the dehumidifiers did help in preventing dust mites, by maintaining a consistently low humidity level. This severely limited the growth of the dust mite populations, which in turn decreased the allergen levels in the homes. While Group 1 experienced considerably less allergens, a smaller dust mite population, and lower reservoirs of dead mites, the remaining homes experienced the opposite. With no humidity control, allergens, dust mites, and dead dust mites all increased.

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Arlian, Larry G. , et al. “Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates.” Wright State University , Department of Biological Sciences, 2001, www.jacionline.org/article/S0091-6749(01)77320-4/pdf
“Dust Allergy.” ACAAI Public Website, American College of Allergy, Asthma, and Immunology , acaai.org/allergies/types/dust-allergy
Hunt, Sherri. “Final Report: Factors Controlling the Dust Mite Population in the Indoor Environment.” EPA, Environmental Protection Agency, 1996, cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.highlight/abstract/706/report/F