Dust/Mite Control

House Dust

House dust is a mixture of many different allergic substances and disintegrated products of various materials found in the home such as carpeting, mattresses, feathers, overstuffed furniture, drapes, blankets and stuffed animals. Other components of house dust include animal and human dander, insect parts, molds, bacteria and mites.

House dust also contains materials that are tracked in from outside the home, such as dirt, pollen and toxic residues. In some homes tested, lead levels in dust vacuumed from carpets far exceeded levels requiring cleanup at toxic dump sites. Pesticides, such as Chlordane, Dieldrin, and DDT have been found in carpets, even though owners denied ever having used these chemicals in or around their home. Samples of house dust taken from different geographic areas may exhibit rather striking differences.

Dust Mites

Dust mites are microscopic, spider-like insects that are believed to be the primary allergen present in house dust. House dust mites can be found in most kinds of natural and synthetic fibers, including carpets, drapes, stuffed furniture, automobile seats, mattresses, pillows and stuffed toys. The bulk of their food is flakes of human skin. Every day the average adult human sheds about 1.5 grams of skin, which is enough food for one million house dust mites. Female mites can lay 25 to 50 eggs with a new generation produced every three weeks.

The greatest source of dust mite exposure in the home is probably the bedroom mattress, which provides the best conditions; warmth, humidity and food for their growth. The waste products that the mites produce are actually the main substance which allergic people react to. Although a dust mite only lives 2 to 4 months, during that time it produces about 200 times its own body weight in waste. This waste product breaks down into tiny particles, mixes with the dust, and then can be inhaled or ingested.

Controlling Dust and Dust Mites

The number of mites found in a home is not necessarily correlated with the cleanness of the home.  House-dust mites prefer places with a relative humidity of 70-80% and temperatures between 68 and 84 Fahrenheit.  They tend to thrive in great abundance in coastal areas in the more temperate climates, including Puget Sound.  Controlling the humidity in your home is probably the most important thing you can do to inhibit mite production.  The dust mites can't survive well when the relative humidity is less than 50%.  However, some experts feel that the humidity should be around 20-30% to keep mites and molds from thriving.  Cooler homes tend to have less mite problems.

Emphasis on mite control is placed on the bedroom, since people spend one-third or more of their day there.  Cotton barrier can be purchased to cover pillows, mattresses and box springs.  These tightly woven cotton materials form a barrier between you and the mites in the mattress, and they can be laundered frequently.  Cotton or wool pillows are recommended and should be covered with allergen proof coverings, such as cotton barrier cloth.  Dacron or synthetic pillows are acceptable if there is no concern about chemical sensitivities.  Vacuuming the mattress can be of some benefit in removing dead mites and their waste products.

Removing excessive amounts of fabrics, especially drapes, carpets and upholstered furniture will cut down on house dust.  Hardwood floors and tile are preferable to carpeting.  Sheets and pillow cases should be laundered weekly and blankets monthly in hot soapy water.  This will kill the mites as well as get rid of the dead mites and waste products. 

High humidity may need to be controlled with a dehumidifier and/or desiccating agents.  Humidity can be measured with a humidity gauge (hygrometer).  Air purifiers containing a HEPA filter are the best choice for removing allergens, as they are able to remove large numbers of dust particles, pollens, dust mites and mold spores.  They should be run continuously.

In severe cases of dust and mite allergy, especially asthma, maintaining a dust-free room for sleeping can be very helpful.  To prepare a dust-free room, remove all furniture, rugs, carpets and drapes.  Empty the clothes closet to clean it and, if possible, store clothing elsewhere.  If clothing is to be stored in the closet, it is best to store it in cotton garment bags.

The dust-free room should probably be cleaned daily with a damp cloth and given a more thorough cleaning once a week.  The woodwork, floors, window sills and door tops should be cleaned with a damp cloth.  Linoleum, hardwood floors or tile are preferable to carpet.  Do not use upholstered furniture or stuffed toys in the room.  Wooden or metal chairs are acceptable.  Cotton rugs or other natural fiber rugs that can be washed are also acceptable.  The patient with severe dust sensitivity should not do the cleaning or be in the room during the cleaning process.  If such patients must do their own dusting, they should wear a particle mask, similar to the kind worn by automotive spray painters, or an activated charcoal surgical mask.

Acaricides (Chemicals that kill Mites)

There are many chemicals that kill mites, but the question is whether or not they are safe enough for home use and whether they can be delivered in such a way that will kill the mites in carpets. Acarosan (benzylbenzoate) is used to eradicate scabies and is effective against house dust mites. The material is applied to the carpet as a powder and then vacuumed. The products may not be effective for more than 6 months. An alternative to this substance is Tannic acid which is present in many natural products, including tea. Tannic acid is available in a spray and is an effective way of denaturing mite allergen and house dust, but does not produce long term effects. Chemically sensitive patients should be cautious or totally avoid the use of chemicals to control mites.

Your bedroom is the room where you spend a third or more of your life. Make it into an oasis, so that your immune system can totally rest, without exposures to allergens or pollutants.