Dust Mite Allergies

These little bugs are so small that between 100 and 500 individual mites live in a single gram of dust. Despite their size, dust mites cause some big problems. Or more specifically, their feces do.

Dust mites live in fabrics like bedding and carpeting that collect the dandruff from human skin. People once believed they were allergic to dust, but researchers now know it's not the dust itself, but rather the mites that live in it that cause the problem. And these mites are everywhere humans live, particularly in bedding, upholstered furniture, carpeting and stuffed animals. They grow best where it's warm and humid; about the only areas where they don't flourish are where it's very dry or the altitude is more than 3,000 feet above sea level. Living on a diet of skin scales naturally shed by humans, each mite produces between 10 and 20 waste pellets each day. And each egg-laying female can increase the population by 25 to 30 mites every three weeks.

These mites are no danger to nonallergic people because they don't bite humans or spread disease. But their numbers have increased dramatically in the past 20 to 30 years (especially during winter months), as more efforts have been made to build "tight" homes and other structures where ventilation is limited and temperatures tend to be warmer.

Here's how to take the might out of dust mites.

 Avoid Panic with Tannic

The best thing you can do to prevent dust mite allergies is to remove their likely homes, such as wall-to-wall carpeting and overstuffed upholstered furniture. But if major redecorating isn't in your plans or budget, try treating carpets and furniture with a spray containing tannic acid, a compound found in oak bark, coffee, cocoa and tea.

Although its effectiveness against mite growth is questionable, tannic acid may help by chemically changing house dust allergens and neutralizing the protein that causes the allergic reactions. You'll have to reapply the spray every month to control mite allergens, and it should be used in conjunction with the chemical benzyl benzoate, which kills the mites. Benzyl benzoate comes as a powder to be applied to carpets every six months and then vacuumed up. (A foam version for furniture and bedding is now sold in Europe and may soon reach the U.S. market, although some studies show it is not effective.)

Dry Up

Mites like it warm and moist, so dehumidifying your home can help. Air conditioning helps reduce humidity, but you may also want to invest in a dehumidifier, especially if you live in a Southern climate. Dust mites do best when the relative humidity is above 55 percent, and grow poorly when it's below 45 percent. When indoor temperatures are close to 80 degrees Fahrenheit, humidity should be lowered below 40 percent. Meanwhile, clean air conditioning filters every month.
“Wooden it be nice"

Big, overstuffed furniture provides the perfect comfort zone for dust and mites. So if you're shopping for new furnishings, choose sleeker, pared-down wooden selections without as much stuffing. And whenever possible, replace wall-to-wall carpeting with wood or sheet-goods flooring and with area rugs that can be easily laundered.

Think Twice Before Filtering Them Out

Installing air cleaners and air filters to remove dust is a costly solution that may not be worth the investment. Air cleaners are available as attachments to your heating system or as portable units that can be moved from room to room. The most effective ones have high-energy particle-arresting (HEPA) filters capable of trapping very small particles. Others use electrical charges, static electricity or ionizers to trap particles. None work well enough, however, to substitute for other steps you can take to cut down on indoor allergens. Cleaners that generate ozone gas have no effect on allergens in the air and may worsen allergy symptoms because the ozone they emit can irritate the respiratory
system.

Wage Battle in the Bedroom

In most homes, the highest concentration of dust mites is in the bedroom, where they love to get cozy in mattresses, pillows and carpeting. However, keeping your bedroom hospital-clean and making some minor adjustments to decor can send mites packing.

• Wash all bedding (including mattress pads, comforters and blankets) in hot water every week to 10 days. Walls, ceilings, closets and the backs and bottoms of furniture should also be cleaned or dusted weekly.
  
• Cover mattresses and pillows in a ready-made air-tight encasement so the mites and their debris can't get out.
  
• Keep a bedspread on your bed all day to collect dust, but carefully remove it from your bedroom before you go to sleep.
  
• Avoid feather or down pillows; instead, use polyester fiber-fill such as Hollofil or Dacron. Although dust mites like synthetic pillows as much as feathers or foam, the synthetic ones can be washed. No matter what you use, all pillows should be encased.
  
• Don't use fuzzy wool blankets; these can't easily be laundered. Other dust collectors include stuffed animals and bed canopies, which should be removed or avoided.

Last Updated: 9/26/2002
The Johns Hopkins University 1996-2003.  All rights reserved.  This information is not intended to provide advice on personal medical matters, nor is it intended to be a substitute for consultation.