I am a meticulous housekeeper, so why does my house harbor dust mites? Should people with asthma encase their bedding? Is it a good idea to invest in an air purifier?
Dust mite is a common indoor year-round allergen; allergy to dust mites has been associated with allergic rhinitis and asthma in children, as well as in adults. If you or your child is diagnosed with an allergy to dust mites, your physician will likely advise you on measures you can take to reduce your exposure to dust mites.
Dust mites are eight-legged arachnids related to the spider family. Their cast skin and fecal matter are two constituents of house dust to which many people are allergic. The dust mite allergen is concentrated in the mites’ fecal droppings. Dust mites live indoors and are present in nearly all homes in areas where the relative humidity is 50% or greater for much of the year. Dust mites are microscopic; you cannot see them without a magnifying microscope.
They are so tiny that fifty to seventy dust mites would fit on the head of a pin! They thrive in warm, dark, humid environments, and live off flecks of human skin. They do not drink free water but absorb moisture from the surrounding environment. They can be found in bedding, in upholstered furniture, and in carpeting and draperies. Their presence in your home in no way implies poor housekeeping.
Dust mites cannot survive at a high altitude or in dry environments. Dryer indoor environments with a relative humidity of less than 40% as well as residence at altitude inhibit the growth of dust mites. Could that be why, several generations ago, some persons with asthma whose treatment included a prescription for relocation to the desert or to the mountains had lessening of their symptoms? Was the relocation no more than a move to an area free of dust mite allergen?
Bedding, upholstered couches and chairs, and carpets are areas where dust mites thrive. Ways to reduce your home’s dust mite burden include addressing increased levels of humidity if present and removing carpeting and heavy cloth draperies. Consider washable curtains or blinds. Avoid stuffed furniture upholstered with fuzzy fabric. An alternative to removing carpeting involves thorough, daily carpet vacuuming with a high-quality vacuum cleaner, possibly one fitted with a high-efficiency particulate air (HEPA) filter.
Steam clean or shampoo carpets and rugs at least once a year. The highest con-centration of dust mites in the home usually is found in the bedroom, which thus demands special attention if you or your child is allergic to dust mites. We sleep for hours each night, head on a pillow or two, wrapped up in sheets, blankets and comforters. Since bedding is a favorite location of dust mites, we are, while asleep, in close contact with dust mite antigen, inhaling allergic material all night long. The good news is that there are simple and effective measures you can take to interrupt the replication of dust mites while decreasing the amount of allergen you come into contact with, especially during sleep.
Recommendations for decreasing exposure to dust mites if you or your child is allergic to them begins with the purchase of special dust mite–proof (impervious) encasings for pillows, mattresses, comforters, and box springs. The allergen-impermeable covers are available from retailers specializing in allergy products. If your physician advises you to encase your bedding, make certain the covers you purchase are rated for dust mite protection. Most covers are of high quality and are unobtrusive; you won’t even know you’re sleeping on one.
They usually require washing once a year and carry a warranty for up to 20 years of use. Once you have encased your mattress, box spring, pillows, and comforter, you can further decrease your exposure to dust mite allergen by taking advantage of the fact that dust mites have a life cycle of 2 weeks and cannot survive elevated temperatures. Simply launder sheets, mattress pads, and washable blankets once a week in water heated to a temperature of at least 130F.
The hotter, the better! If the water does not reach at least 130F (55C), the dust mites are only getting a bath. Dust mites also set up housekeeping in carpeting and in upholstered furniture. If possible, the bedroom should have a wood or tile floor and blinds rather than curtains or drapes. Washable cotton throw rugs can be used in the bedroom to minimize dust mite antigen, provided that you launder the rugs. Stuffed animals or dolls are potential dust mite collectors, and therefore should ideally be kept in a covered toy chest in a room other than the bedroom.
Stuffed animals are an abundant source of dust mite allergen, and many children love to collect and sleep with them. Encourage your child to keep the collection in a location other than the bedroom and consider identifying one special stuffed toy to sleep with. Then, if possible, launder the favorite in your washing machine in water hotter than 130F at least every 2 weeks (every week is best) in order to interrupt the mites’ reproductive cycle. Unfortunately, not all stuffed animals are machine washable. Despair not! Plan B involves placing the furry toy in a sealable plastic bag, like a Ziploc bag, sealing it, and placing the bag in your freezer for 12–24 hours once a week.
Should someone with dust mite allergy invest in an air purifier? Be sure to ask your physician or allergist before buying one. Among the options currently available, only a few have been studied in the medical (as opposed to the industrial) literature. Machines that are designed to filter the air in an enclosed space through a fine, HEPA filter are, if used correctly, very efficient in trapping particles of a defined size (usually as small as 0.3 microns).
HEPA filters thus reduce the airborne concentration of microscopically small airborne particles, including many aeroallergens, like pollens and dust mites. HEPA-filtering machines must be selected based on the square footage of the enclosed space they will filter. The machines usually contain both a carbon prefilter and a true HEPA filter. The prefilter should be changed every 3–6 months, and the HEPA filter should be replaced every year. HEPA filters are expensive but effective.
HEPA filter units do not require much maintenance, apart from filter changes, and they are engineered to run 24 hours a day. They have the disadvantage of being noisy, and they do tend to dry the ambient air. The correct way to run a HEPA unit is to close the room’s windows and doors and set the unit’s fan on high when you are not home. When you are in the room, at night, for example, set the unit’s fan on the highest level you can tolerate from the perspective of noise.
Gemma’s Comment:
Unfortunately, many standard leases require that three quarters of the floor in every room be carpeted to reduce sound in adjacent apartments, and daily vacuuming is a big task for the housewife with small children. Which is only to say that taking charge of one’s asthma is not an easy matter.