House Dust Mites

House dust mites are microscopic animals belonging to the arthropod class, Arachnida, related to ticks, spiders and scorpions. Barely visible to the eye, yet present in most indoor environments with high humidity, their major impact is on human health. House dust mites are agents in allergenic reactions, notably asthma.

Common types

The most common species of house dust mites in the U.S. are the American dust mites (Dermatophagoides farinae) and European dust mites (Dermatophagoides pteronyssinus).

Biology

The largest individuals are the females that measure about 1/64th of an inch. Microscopic examination reveals that the mature mites have eight legs, while the pre-adult stages have six (larva) and eight (protonymph, tritonymph).

Because of the house dust mites’ minute size, distribution data is not as readily available as for larger pests. Typically found in beds, pillows, sofas and other soft furnishings and carpets, their presence has been established across the US.

Mites feed on organic matter in house dust, which consists predominantly of human skin scales and also of fungi and food or waste particles. Mites absorb moisture through their skin, so higher relative humidity favor mite population growth (and low humidity limits their distribution.) It is likely that wherever a reasonable level of humidity is maintained, dust mites will be found. Dust mites have been found in mattresses at the rate of up to 12,000 mites per gram. The average life span of the dust mite is 80 days, during which the mature female lays 1-2 eggs per day. At 80 degrees Fahrenheit and 75% relative humidity, development from egg to adult takes about 30 days.

Health issues

House dust mites are a significant factor in causing allergies in humans. Five percent of the population is believed to be allergic to house dust- and one of these types of allergic reactions can be asthma attacks. The growing prevalence of asthma in the U.S. affects 14-15 million people, 4.8 million of them under 18 years of age.

Asthma caused 198,000 hospitalizations and 342 deaths among people less than 25 years in 1993. Some 45-85% of asthmatics has been shown by skin patch test to be sensitive to mites, compared to 5-30% for the general population.

House dust mites are major producers of the allergens-substances that cause allergies-in dust, known medically as Group 1 human allergens. Symptoms of house dust allergies include asthma, runny nose, watery eyes, sneezing, and breathing difficulties and skin inflammation.

Dust mites Control

Because house dust mites are virtually invisible yet present almost everywhere, the most efficient control will come from common sense and consistent cleaning to reduce their potential for allergenic reactions.

Lower humidity by airing or mechanically dehumidifying rooms, beds and closets. Replace pillows on a regular basis. Keep house dust to a minimum by vacuuming, washing to remove dirt and dust, and occasionally steam cleaning carpets.

In addition to thorough and regular cleaning, control of dust mites with suitable mite control products also may reduce their allergenic potential in the home.

There are more varied types of products for dust mite control than probably any other type of arthropod, probably because of mites’ direct link with allergies. These include pillow case covers, bed mattress covers, and various types of home filters and vacuum cleaner filters.

In addition, various acaricidal products will control dust mites. These include carpet sprays and powders that help to reduce the dust mite population. Products for upholstered furniture address a favorite dust mite habitat. Numerous consumer cleaning products help to reduce the amount of dust and dirt in the home and remove some of the allergens. These include a range of carpet cleaning products, furniture polishes, dust removers and any household cleaning product that will remove some of the dust and debris contributing to allergies.