Dust Mites

Dust mites are microscopic creatures that belong to the same class (Arachnida) as spiders and ticks (they have eight legs, not six like insects). They feed primarily on dead skin cells regularly shed by humans and animals. Dust mites are found where their main food source accumulates, such as in beds and carpets.

Unlike insects such as cockroaches, mites are not capable of ingesting water; in order to obtain water, they must absorb it from the air. For this reason, they thrive in humid environments, ranging from 55% to 75% relative humidity. Ideal temperatures for dust mites are between 68° and 77° F. The growth of dust mites can vary on a seasonal basis, or from room to room within a house, depending largely on variations in relative humidity, availability of food sources, and temperature. Mites take about one month to develop from an egg into an adult and have an adult life span of about two to four months. A single adult female may lay up to 100 eggs.

Health Impacts

Mite waste products contain an allergen (a substance that causes an allergic immune reaction) that, according to the Asthma and Allergy Foundation of America, adversely affects about 20 million Americans. Sensitive individuals become exposed to this allergen when they inhale household dust, which contains dust mites and their waste products. Exposure to dust mites can trigger an attack in an asthmatic who is sensitive to the dust mite allergen. (Other asthmatics may not be affected by dust mites.) For persons allergic to dust mite allergen, exposure can cause allergic rhinitis (hay fever), which is characterized by nasal congestion, itching, and sneezing. In addition, exposure to dust mites may cause children who are predisposed to develop asthma to do so. (This predisposition is not fully understood, but appears to depend upon a combination of hereditary and environmental factors.) For more information on asthma and allergies, see Asthma, Allergies, and Respiratory Illnesses.

Common Locations

Dust mites thrive in places where dead skin cells are most likely to be found: on mattresses, pillows, bedcovers, carpets, upholstered furniture, stuffed toys, clothes, or other fabric items in the home.

Reducing Exposure

While it is impossible to have a dust-free home, it is possible to live in a home that minimizes dust that is carried in from the outside and to avoid conditions that can promote allergens in dust.

Use materials that are easy to clean. This will make it more difficult for dust mites and mold spores to thrive.

  • Dust is easily removed from smooth and cleanable surfaces (smooth flooring such as wood, tile, linoleum, and vinyl) through vacuuming and mopping.
  • Use a vacuum cleaner with high filtration features (high efficiency or HEPA filter).
  • Carpets pose several problems. They are generally more difficult to vacuum effectively than hard surfaces. Also, carpets and the sponge-like pads often installed under carpet can trap moisture once they become wet (due to a plumbing or water leak, flood, or condensation), providing a fertile setting for mold and dust mites.
  • Short- and closed-loop-pile carpets (such as commercial grade carpet) are typically easier to clean than loose-pile carpets where dust and dirt falls through to the underlying material.

Clean fabrics and other dust mite havens. The following measures will kill dust mites and reduce allergen levels.

  • Wash sheets in soapy water at 130° F every one or two weeks to kill dust mites. Take blankets to the dry cleaner, hang them outdoors once a year, or wash them frequently.
  • Cover conventional mattresses and pillows with allergen-impermeable covers or dust mite covers (micro-porous material to prevent infestation).
  • Wash soft toys and stuffed animals regularly in hot water, followed by thorough drying. The heat will kill off the mites.
  • Shampoo, steam clean, or beat non-washable rugs and carpets once a year. This removes large particles missed by the vacuum cleaner.

Reduce moisture and maintain a low relative humidity in the home. Since dust mites cannot drink water, they need to absorb it from the air, which is why they thrive in humid conditions. Reducing the humidity in your home will make it less hospitable to dust mites, which do not thrive below 60% relative humidity. It may not be feasible to completely eliminate dust mites from homes in moderately humid climates.

One way to help reduce moisture in the home is to run a bathroom and kitchen fan that exhausts to the outside after showering/bathing or cooking.

Dust Mite Resources

HouseDustMite.org– Helpful animations and answers to frequently asked questions about dust mites

US Environmental Protection Agency – Dust Mites

University of Nebraska Cooperative Extension in Lancaster County, “House Dust Mites.”

P. Vojta, S. Randels, J. Stout, M. Muilenbert, H. Burge, H. Lynn, H. Mitchell, G. O’Connor, and D. Zeldin, Environmental Health Perspectives, “Effects of Physical Interventions on House Dust Mite Allergen Levels in Carpet, Bed, and Upholstery Dust in Low-Income, Urban Homes,” 815-819 (August 2001).

Asthma No Attacks Hotline: 1-866-NO-ATTACKS (1-866-662-8822)

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