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What are dust mites?

Skin cells and scales, commonly called dander, are often concentrated in lounging areas, mattresses, frequently used furniture and associated carpeted areas, often harbor large numbers of these microscopic mites. Since the average human sloughs off 1/3 ounce (10 grams) of dead skin a week. That gives dust mites a lot to eat. Cats and dogs create far more dander for dust mites to eat.

A typical mattress can contain tens of thousands of dust mites. Sick yet? Nearly 100,000 mites can live in one square yard of carpet. Ready to convince your spouse to start bathing regularly? Did you know a single dust mite produces about 20 waste droppings each day, each containing a protein to which many people are allergic. Yuck! The proteins in that combination of feces and shed skin are what cause allergic reactions in humans. Depending on the person and exposure, reactions can range from itchy eyes to asthma attacks. And finally, unlike other types of mites, house dust mites are not parasites, since they only eat dead tissue. Gross, but true.

Where do they live?

Beds are a prime habitat (where 1/3 of life occurs). A typical used mattress may have anywhere from 100,000 to 10 million mites inside. (Ten percent of the weight of a two year old pillow can be composed of dead mites and their droppings.) Mites prefer warm, moist surroundings such as the inside of a mattress when someone is on it. A favorite food is dander (both human and animal skin flakes). Humans shed about 1/5 ounce of dander (dead skin) each week. About 80 percent of the material seen floating in a sunbeam is actually skin flakes. Also, bedroom carpeting and household upholstery support high mite populations.

The University of Manchester performed a 2005 medical study of pillows that found up to 16 species of fungi in a single pillow. They tested feather and synthetic pillows in a range of ages, finding thousands of spores of fungus per gram of pillow ; more than is found on an average used toothbrush.

Are they harmful?  What do they do?

For most people, while they are disgusting, house dust mites are not actually harmful. However, the medical significance of house dust mites arises because their microscopic cast skins and feces are a major constituent of house dust that induces allergic reactions in some individuals. There is a genetic predisposition to dust mite allergies, but like many allergies it can also develop over time. The constituents of house dust are show in the following figure:

Organisms in household dust:

For those individuals, inhaling the house dust allergen triggers rhinitis allergica or bronchial asthma. People with allergies to house dust usually also have allergic reactions to house dust mite fecal material and cast skins. Studies have shown that the most potent house dust allergens can be extracted from the feces produced by dust mites. Other important allergen-producing organisms that are found in house dust are found in Figure 1. The rest of this fact sheet, based on Chapter 10, "Mites," in Common-Sense Pest Control by Olkowski, Daar and Olkowski, will discuss biology of dust mites and will emphasize non-chemical control tactics. An allergist, a medical doctor specially trained to treat allergies, should be consulted for proper diagnosis and treatment of allergies. 

One of the most strongly allergenic materials found indoors is house dust, often heavily contaminated with the fecal pellets and cast skins of House Dust Mites. Estimates are that dust mites may be a factor in 50 to 80 percent of asthmatics, as well as in countless cases of eczema, hay fever and other allergic ailments. Common causes of allergy include house dust mites, cat dander, cockroach droppings and grass pollen. Symptoms are usually respiratory in nature (sneezing, itching, watery eyes, wheezing, etc.), usually NOT A RASH. However, there are reports of a red rash around the neck. Other allergic reactions may include headaches, fatigue and depression.

The wheeze-inducing proteins are digestive juices from the mite gut which are quite potent. An exposure to the mites in the first, crucial year of life can trigger a lifelong allergy. There is no cure, only prevention. One must control house dust mite levels.

Beds are a prime habitat (where 1/3 of life occurs). A typical used mattress may have anywhere from 100,000 to 10 million mites inside. (Ten percent of the weight of a two year old pillow can be composed of dead mites and their droppings.) Mites prefer warm, moist surroundings such as the inside of a mattress when someone is on it. A favorite food is dander (both human and animal skin flakes). Humans shed about 1/5 ounce of dander (dead skin) each week. About 80 percent of the material seen floating in a sunbeam is actually skin flakes. Also, bedroom carpeting and household upholstery support high mite populations.

How to Recognize the Symptoms of Allergies to Dust Mites

The protein substances in the dust mite feces produces antibodies in humans who are allergic when these are inhaled or touch the skin. These antibodies cause the release of histamines which causes to nasal congestion, swelling and irritation of the upper respiratory passages. Typical symptoms of an allergy to dust mites includes some or all of the following:

A doctor can use skin tests and blood tests to confirm a suspected dust mite allergy.

Since dust mites are present all year round, the symptoms of the allergy can be present at any time of the year, but are worst  in months and seasons when the house is closed and the indoor humidity and temperatures are high (which, depending upon the household's use of heating and air conditioning, can be any time of the year). The dried dust mite feces becomes airborne when someone walks over a rug, sits down in a chair, or shakes the bed clothes, making allergic person's symptoms worse.

What else makes the symptoms worse?

Identification

House dust mites, are too small to be visible to the naked eye; they are only 250 to 300 microns in length and have translucent bodies. It takes at least a 10X magnification to be able to correctly identify them. The adult mite's cuticle (covering) has simple striations that can be seen from both the dorsal (top) view and from the ventral (bottom) view. The ventral view of the house dust mite reveals long setae (hairs) extending from the outer margins of the body and shorter setae on the rest of the body. Through the microscope, one will see many oval-shaped mites scuttling around and over one another. There are eight hairy legs, no eyes, no antennae, a mouthpart group in front of the body (resembles head) and a tough, translucent shell, giving a "fearsome appearance."

Biology and Life Cycle

Adult females lay up to 40 to 80 eggs singly or in small groups of three to five. After eggs hatch, a six-legged larva emerges. After the first molt, an eight-legged nymph appears. After two nymphal stages occur, an eight-legged adult emerges. The life cycle from egg to adult is about one month with the adult living an additional one to three months.

The diet is varied with the primary food source, consisting of dander (skin scales) from humans and animals. However, needed nutrients can be provided from fish food flakes, pet food, fungi, cereals, crumbs, etc. Many mite species live in bird's nests, in barns, among stored grain, straw, etc.

House dust mites are cosmopolitan in distribution with much of the research previously done in Europe.

One of the major limiting factors in mite survival and population development is the availability of water for sorption. Highest mite densities occur in the humid summer months and lowest in drier winter periods. Dust mite populations are highest in humid regions and lowest in areas of high altitude and/or dry climates.

Due to the large quantity of skin scales sloughed off daily by humans, mites have an abundant food supply. Dust mite antigen levels are measured in bed dust, floor dust, and room air samples. Detection in room air was best during cleaning and bed-making activities.

Detection

House dust mite presence is often suspected before they are actually seen and accurately identified. Requests for control often come from individuals who have been diagnosed by medical personnel as allergic to the house dust mite or the allergens produced.

The presence of house dust mites can be confirmed microscopically which requires collecting samples from mattresses, couches or carpets. Also, it requires the use of a microscope with sufficient magnification and the technical ability to recognize house dust mites under the microscope. In general practice, testing is unnecessary.  dustmites are extremely common in household environments. They virtually always show up in a test, so testing just adds expense.  A better question than "are dust mites present?" is "How can I control or remove them?"

What Can Your Do?

Control measures and Sanitation

Recommendations focus on "dust control." One must reduce the concentration of dust borne allergens in the living environment by controlling both allergen production and the dust which serves to transport it. For the bedroom environment you will want to use some or all of the following methods.  We have listed them in order of practicality combined with effectiveness.:

1. The most effective means is to enclose the mattress top and sides with a plastic cover or other dust mite impervious cover (available here, click on allergy bedding on the left in the new page), thoroughly vacuuming mattress pillows and the base of the bed. Put an airtight plastic or polyurethane cover over your mattress. This is the method recommended by Consumer Reports (see their article here). This tip is number one for a reason: it is in your bed (including the baby's crib) that you are closest to the mites and their feces and enclosing the mattress and pillows in a dust mite cover virtually eliminates the mites here.  There is a website, The Allergy Store, that we recommend that sells allergy controls, like the dustmite-proof fitted sheets. Mattresses covered with "fitted sheets" help prevent the accumulation of human skin scales on the surface.  These sheets have the advantage of being waterproof, too, which helps protect your mattress from spills, babies and toddler's waste, too.

2. Wash your sheets and blankets in very hot water at least every two weeks. Wash your pillow every week or put a plastic cover on it. (The pillowcase goes over the plastic cover.)  How hot is hot? The water used to wash your sheets and blankets should be at least 130°F (54°C). Set your washing machine to it's hottest setting.  If the water doesn't seem to be coming out hot, you may want to check your hot water heater - you may not realize that most household hot water heaters have a knob that can adjust the temperature of the water it produces. For fabrics that may not be washed in hot water; just pop it into the freezer for 24 to 48 hours to kill dust mites.
   And for those who travel and stay in hotels (or with less hygienic friends and family): Take a dust mite impervious cover (available here), along for when you stay at hotels - just think how disgusting their pillows must be!

3. Use Synthetic fabrics: Replace feather and down pillows with those having synthetic fillings. Replace woolen blankets with nylon or cotton cellulose ones. And don't forget the children's stuffed animals: be sure to get washable stuffed animals in the future!

4. Reduce Temperature and humidity: Dust mites love warm, humid conditions, above 70 F (21 C) and 50% humidity
   Temperature: Keep the thermostat in the house below 70 degrees.
   Humidity: Effective control of mites would require the maintenance of relative humidity's below 50 percent.  A study (Feb 2005) by Kingston University (London UK) shows that simply by leaving your bed unmade each morning, with the sheets to be exposed to the air, allows the sheets to dry out, and substantially reduces the numbers of dust mites.
   Some researchers feel it is important to focus on decreasing indoor humidity, especially during the winter period to reduce dust mite populations. One might forsake humidifier use during winter periods (or limit it to the bedroom only at night, then ventilate the room during the day). It will help to use dehumidifiers during high-humidity periods, or use central air conditioning. So if you use a humidifier in the winter, adjust it to produce 35% to 45% humidity.  Some humidifiers have  this control built in; with others, you'll need a humidity gauge (usually sold with a thermometer at Costco, Sam's Club, Wal-Mart, Target, etc.). And generally, homes that have their air conditioners on constantly in the summer and dry heat in the winter have lower mite counts than non-air conditioned homes.

5. Clean weekly: Weekly change pillowcases, sheets, and under blankets, and vacuum the bed base and around the covered mattress.   Clean flooring: Use a damp mop or rag to remove dust. Never use a dry cloth or broom, since this just stirs up mite allergens.

6. Clean daily: Daily damp dust the plastic mattress cover.

7. Frequently wash all bedding (blankets, mattress pads and comforters) in hot water (130 degrees F [or 60°C] weekly). Cold and warm water won't kill mites. Also wash curtains.

8. Remove carpeting and replace with wood, tile, linoleum, or vinyl floor covering. Remove cloth drapes and blinds. (If you have carpet, vacuum every day.) Vacuuming your carpets and upholstery every week can help. See the caution about vacuuming below under tips. Vacuums with high-efficiency filters pick up more dust mites, but even standard vacuums work well enough. 

9. Freezing and sunlight kills mites but does not remove their residue.  In addition to freezing temperatures and washing items in temperatures greater than 130 degrees F, extended exposure to sunlight, and low levels of humidity also destroy the mites.

10. Children's soft cloth toys: Regularly place soft toys in the freezer for 24 hours before you wash them, or wash them in hot water. Removing them, or at least reducing the numbers of them on the beds, will help, too.

11. Air Purifiers: While it is better to stop the dust mites at the source, reducing the dust levels in the air is a good secondary measure. Some pest control firms sell air purifiers to eliminate the food source of house dust mites. Although ozone air purifiers emit a low level of ozone (activated oxygen) that attaches to fungus, mold, and bacteria on skin flakes, EHSO does not recommend ozone generators (neither does the US Food and Drug Administration).  The same ozone that is oxidizes the dust mites is bad for your health. Air purifiers that use HEPA filtration are more effective and safe to use.  Various types of air purifiers can be attached to the central air return to decrease irritants. Most filters remove 50 to 70 percent of material. HEPA filters will remove up to 99 percent of the material; not just dust mite feces, but also all types of other allergens, like animal dander, dust, pollen, cockroach feces, etc... See this page for information about selecting an air purifier.

12. Furnace Air Filters: Clean or replace the air filters on your furnace or air conditioner at least once a month. Filters that are rated to trap allergens are obviously more effective than plain spun glass.
    

Multiple Allergies

It should also be noted that people are rarely allergic to only dust mites.  When a person has an allergy to dust mites, they are usually also allergic to other allergens.  In a report on WebMD (April 2008), Allergist Jonathan A. Bernstein, MD, of the University of Cincinnati says, "You have to recognize that people can be sensitive to multiple allergens -- as well as to non-allergic triggers such as odorants, irritating chemicals, tobacco smoke, mildew, and things of that nature, so these studies with just one or even two or three interventions are fraught with limitations. Just to target dust mites and then to say these interventions don't work is out of context with patients' real lives."

In that WebMD article, which initially implies that dust mite prevention methods are ineffective, the researchers insist that "reducing allergens in the home and in the office will help patients suffering from dust-mite allergy and asthma." They say reducing dust mites is a good place to start. In other words, if you use methods that

Then you will not only reduce dust mite populations and their allergens, but also many other allergens.  This comprehensive approach will help reduce many allergic symptoms.

Get De-Mite, laundry additive to eliminate dustmites in cold or warm water washes (click on the "Laundry" link on the left that, in the window that opens).

De-mite® laundry additive eliminates dust mites in bedding and washable clothing that laundering in regular detergent alone does not do. Until now the only way to rid your clothing of dust mite allergens was to wash them in hot water. That great if all your clothes were white. De-mite® is an additive that you can add to your favorite detergent. This product works is just as effective in cold water as it is in hot.
Easy application. Fill the plastic dosage cup 3/4 full and pour it in. each 8 oz bottle treats 12-13 loads of wash.