Allergy & Asthma Triggers in the Home

House Dust and Dust Mites

House Dust

House dust is everywhere. It is part of our life! House dust is a component of who you are. House dust is not just dirt but a mixture of potentially allergenic materials, such as:

• fibers
• plants and insect parts
• food particles
• hair, animal fur and feathers
• mold spores
• dried saliva and urine from pets
• pollens
• flakes of human and animal skin
• dust mites

The more time you spend indoors, particular in the fall and winter, the greater your exposure to house dust allergens. House dust allergy is common even in clean homes.
House dust is a major cause of year-round runny or stuffy nose, itchy, watery eyes and sneezing for allergy sufferers. Dust can also make people with asthma experience wheezing, coughing and shortness of breath.

House dust is a mixture of many substances. Its content varies from home to home, depending on the type of furniture, building materials, presence of pets, moisture and other factors. A speck of dust may contain fabric fibers, human skin particles, animal dander, microscopic creatures called mites, bacteria, part of cockroaches, mold spores, food particles and other debris. Of these, animal dander, house dust mites, and cockroaches are the most common culprits. A person may be allergic to one or more of these substances, and, if exposed to the dust, will have an allergic reaction.

No. However, a dirty house can make a house dust allergy problem worse. Normal housekeeping procedures may not be enough to get rid of house dust allergy symptoms. This is because many of the substances in dust cannot be removed by normal cleaning procedures. For example, no matter how vigorously you dust or vacuum, you will not reduce the number of dust mites present deep within carpeting, pillow, and mattresses. Vigorous cleaning methods can put more dust into the air, therefore making symptoms worse.

Tiny microscopic creatures called dust mites are an important cause of allergic reactions to house dust. They belong to the family of eight-legged creatures called arachnids. This family also includes spiders, chiggers and ticks. Dust mites are hardy creatures that live well and multiply easily in warm, humid places. They prefer temperatures at or above 70 º F with a relative humidity of 75-80 percent and die when the humidity falls below 40-50 percent. They are rarely found in dry climates.

As many as 10 percent of the general population and 90 percent of people with allergic asthma are sensitive to dust mites. Recent studies suggest that at least 45 percent of young people with asthma are allergic to dust mites.

There may be as many as 19,000 dust mites in one gram of dust, but usually between 100 and 500 mites live in each gram. (A gram is about a weight of a paper clip). Each mite produces about 10-20 waste particles per day and lives for 30 days. Egg-laying females can add 25-30 new mites to the population during their lifetime.

Mites eat particles of skin and dander, so they thrive in places where there are people. Dust mites don't bite, cannot spread diseases and usually do not live on people. They are harmful only to people who become allergic to them. While usual household insecticides have no effect on dust mites, there are ways to reduce exposure to dust mites in the home.

Molds are commonly found in outdoor air. However, any house can develop a mold problem given the right conditions. You might not see it growing on the walls, but it may still be present in your home. Molds require two factors to grow indoors:

1. Free moisture that can occur in the form of relative humidity above 50 percent, leakage from pipes or foundations, or any ongoing source of water.

2. Something to grow on. Molds particularly like to grow on wallboard, wood, or fabrics, but will grow virtually any place if they are given a chance.

Molds spread by producing spores that can become airborne. These spores end up in house dust where they grow. Dust from mold-contaminated houses can cause symptoms if a mold-sensitive person inhales it.

Dust mite populations tend to peak in July and August, and their allergen levels stay high through December. This is the time where forced-air heating systems tend to blow dust particles into the air and particles become airborne. Mite allergen levels are lowest in late spring. Some dust mite sensitive people report that their symptoms get worse during the winter. That's because mite fecal particles and pieces of dead mites, both of which trigger dust mite allergy, are still present. Mold levels tend to peak during the summer months depending on where you live since some tropical areas have molds year-round. There is also evidence that cockroaches have a seasonal pattern, peaking in the late summer.

If you think you may have an allergy to house-dust, consult an allergist-immunologist. To pinpoint the cause of your symptoms, the allergist may ask questions about your work and home environment, eating habits, family medical history, frequency and severity of symptoms, exposure to pets and a variety of other questions. Your allergist may test you for allergy by doing skin tests, which involves pricking the skin or injecting it with different allergens and observing for a reaction. A positive reaction (a raised welt with redness around it) may indicate that you are allergic to that allergen. Occasionally, your allergist may order a blood test instead of the skin test to confirm the diagnosis of allergy.

House dust avoidance works best to relieve symptoms.
The three basic treatments for dust mite allergy are:

• Dust mite avoidance
• Prescription medications
• Allergy shots (immunotherapy)

How do I avoid house dust?
Environmental control of house dust exposure is best done if you know what allergens present in your home's dust are causing the problem. Dust mites can be difficult to remove completely from your home. However, you can follow certain anti-mite procedures that will reduce mite populations and your exposure to them, thereby reducing your symptoms. Some of these procedures are difficult and you may not need to do them all. Ask your allergist which ones will be most helpful for your situation.

Help is on its way!
The ABC's of reducing house dust mite allergies.

• Clean thoroughly at least once a week
• Seal the mattress, pillows, and duvet/comforter in Allergen Barrier encasings. Seal the boxspring in a vinyl encasing.
• Wash all bed linens weekly in hot water (130 º F / 55 º C ) to kill the mites.
• Remove all dust-collecting objects, such as books, ornaments, and wall hangings from the bedroom.
• Consider having wooden flooring instead of carpet.
• Reduce humidity levels if possible.
• Keep airborne dust to a minimum by using a damp cloth when dusting.
• Replace heavy curtains with lightweight/washable ones, roller blinds/shades or vertical blinds.
• Never allow pets in the bedroom area.
• Remove upholstered furniture and stuffed toys.
• Avoid sleeping or lying on upholstered furniture.
• Maintain and clean the furnace and all air ducts.
• Use the appropriate HEPA air cleaners to remove airborne allergen particles.
  (Four air changes per hour is recommended).