Allergy Control: How to Defeat Dust Mites, a Big Trigger

Allergy Control: How to Defeat Dust Mites, a Big Trigger

They prowl our beds and sofas, invisible to us but hugely allergenic. Here’s the lowdown on dust mites, and what you can do to protect your family.

THEY are tiny enough that you can’t even see them with the naked eye – but as millions of people around the world can attest, dust mites pack a big wallop when it comes to allergies and asthma. In fact, it’s estimated that 84 percent of U.S. homes contain dust mite allergen, and it’s one of the most common and potent allergy and asthma triggers .

So what exactly are these little freeloaders? Why do they love us so much? How come they make us so miserable? And most importantly, which ways of getting rid of them actually work? You might be surprised.

The Mite Life

Some medical websites claim that dust mites are so tiny, there can be as many as 40,000 of them in a single speck of dust. But that’s far from the truth, according to Dr. Jay Portnoy, director of allergy, asthma and immunology at Children’s Mercy Hospital and professor of medicine at the University of Missouri in Kansas. Portnoy, who co-authored extensive guidelines for physicians who treat dust mite allergies, says the mites are small, but they are almost the same size as many dust particles. In fact, they are just outside our range of vision so they can be seen with even the most basic microscope.

While they look like they could be distant relatives of the beetle, dust mites are not actually insects; they are arachnids with close biological ties to spiders, crabs and shrimp. But unlike their web-building and seafaring cousins, dust mites’ favorite food is skin scales, which is why they flock to mattresses, carpets and upholstered furniture where people’s dead skin tends to accumulate. (Their scientific name is Dermatophagoides, which means “skin eating.”)

Dust mites live roughly two to four months, and are hungry for moisture; in fact, they need a steady supply in order to survive. By weight, dust mites are roughly 75 percent water, and they can’t drink, so they rely entirely on absorbing moisture from the environment around them through glands at the base of their front legs. That’s why in dry climates, dust mites are almost nowhere to be found – even in dusty spaces.

“They’re basically bags of water with legs, so they don’t tolerate drying out,” says Portnoy, who worked with 22 other top experts to produce Environmental Assessment and Exposure Control: A Practice Parameter, Dust Mites for physicians in 2013. “So it can be very dusty in Denver, but they don’t have any dust mites because it’s persistently so dry that dust mites don’t survive. In Florida, it’s so humid that you can’t get rid of them. They’re everywhere.”

In most climates, mite populations increase in summer, when humidity is high, and peak in the fall – which experts suspect is part of the reason asthma rates are so high at that time of year. They begin to taper off in winter when it’s colder and drier. By late winter and early spring, populations are usually at their lowest.

So What’s the Problem?

They also poop a lot – roughly 20 times a day – and those fecal pellets are the major source of the powerful allergens they produce. The tiny pellets are just the right size to become easily airborne, too, so even walking across a carpet, sitting on a sofa, or moving a pillow can send them flying – and into people’s airways. Once the pellets get kicked up, they don’t settle back down for 15 to 30 minutes.

“When mites eat skin cells, they have enzymes they use to digest them. And when the little fecal pellets come out, the enzymes are in those pellets and they serve as very potent allergens,” says Portnoy. “And when you inhale it’s just the right size to get deep into the lungs and cause an asthma attack.”

But the little pests aren’t only causing problems with the air we breathe; in rare instances they have also stirred up trouble with our food. Dust mites and other types of allergen-producing mites can contaminate grain flour, and systemic reactions from hives to anaphylaxis have been reported in dust mite-allergic people after eating pancakes, grits, beignets and other grain-containing foods.

The allergens are so stable that cooking doesn’t help; as a result, Portnoy recommends that people with mite allergies keep their flour in sealed plastic containers – and that people who experience allergic reactions to grain flour, but test negative for allergy to the grain, should also be tested for allergy to mites.

There’s also an intriguing shellfish link: tropomyosin, one of the major allergenic proteins in dust mites, is also present in shrimp, lobster and crab. A few studies suggest an allergy to dust mites may make some individuals more susceptible to reacting to a crustacean dinner. But the connection is unclear, and the new guidelines don’t recommend avoiding shellfish simply because of a dust mite allergy. Allergists point out that dust mite allergy is far more common than shellfish allergy, so one does not necessarily lead to the other.

How to Get Rid of Them

If dust mites need moisture, and they can’t survive in dry environments, just pick up a portable dehumidifier or two and your problem will be solved, right? Not true, says Portnoy, who notes studies have found that the stand-alone dehumidifiers aren’t up to the task, because as soon as you open the door to a room where the dehumidifier is running, moisture moves in, and mites require very little to sustain themselves. Even in a fully dehumidified house, having a shower or cooking without a vent fan running can introduce more than enough moisture to sustain dust mites for days.

So in the human versus mite fight, what actually works? Portnoy says a whole house dehumidification system definitely makes a difference; but there are other key ways to significantly reduce the dust mite population. Buying a hygrometer, a relatively inexpensive tool that measures humidity, is a good start, because then you’ll know just how much you need to dry out. (Below 50 percent humidity, few mites can survive.)

The pesky arachnids love warm, moist environments that come with limitless room service – skin cells – so first and foremost, people with allergies should cover their mattresses, box springs and pillows using allergy encasings made from fabric that’s tightly woven. Mites can make their way through the more loosely woven or non-woven protectors, so it’s important to check the manufacturers’ fine print.

Sheets, pillowcases and comforters must be washed regularly – but the guidelines give contrary advice to a long-held belief about water temperature, they say you don’t necessarily need to wash in piping hot water, because the majority of the mites die from drowning, not heat. The difference is so negligible, in fact, that the guidelines say the scalding risk of very hot water outweighs the potential mite-killing benefits. (It should be noted that some studies favor very hot water as a means of killing dust mites’ eggs, which are hardier.)

But mites don’t like it hot, either: a dryer at high heat will kill them off, as will a stint in the freezer – so it’s a good idea to give kids’ plush toys a tumble, or a little chill out time. (If you put them in the freezer, however, Portnoy advises first putting them in a sealed plastic bag so they don’t get damp when they thaw.)

In the rest of the home, the key is to avoid giving the ubiquitous creatures a comfortable place to set up shop. They can-not live on hard or non-porous surfaces, so hard surface flooring such as wood or tile is ideal, as is furniture made from wood or covered in leather.

Carpeting, rugs, and upholstered furniture should be avoided altogether, because they’re like dream homes for dust mites: Carpeting, rugs, and upholstered furniture should he avoided – they’re like sheltered dream homes for dust mites. warm, moist, sheltered, porous and full of food. “They’ll climb inside and live in there, and it does cause harm,” says Portnoy.

“When you sit down on an old couch you’re getting a big puff of dust up into your face. Most people don’t sleep on their upholstered furniture, so the bed is the biggest problem, because you’re spending eight hours a day there. But if you sit in front of the TV on a chair that’s upholstered, you’re getting that exposure, too.”

A must-have for every home where there are allergies and asthma, says Portnoy, is a vacuum with a HEPA filter; and if you have carpeting, a vacuum with a beater bar that can kick the mites, and their nasty pellets, out of the fibers and into the cleaner.

“Carpeting provides shelter and it also serves as a reservoir – so even if you get rid of the mites, the reservoir will continue to release the allergens,” says Portnoy He views vacuuming as so essential that his clinic has donated vacuums to some families in need.

“You need to use a high-efficiency vacuum cleaner, such as a cyclonic vacuum or one with a HEPA filter. If the vacuum has a low-efficiency filter it serves as an allergen dispersal service. It goes in and comes right about out again. It doesn’t help.”

The Good News

There is good news, especially for new parents: Portnoy and his expert colleagues think that dust mite allergies can be prevented, or at least significantly reduced, if parents do their best to prevent dust mite exposure, especially during the first six months of life.

And if you already are allergic to dust mites, allergy shots can significantly reduce symptoms for many years at a time.

Portnoy acknowledges that minimizing exposure through dust mite covers, a good vacuum cleaner, bare floors and non-porous furniture might hurt the pocketbook at first – but he and his colleagues did a cost analysis and found that skipping those fixes means bigger bucks in the long run, because people end up buying more pricey antihistamines and asthma medications.

“Medicine is something you buy all the time, so it’s a continuing cost, whereas many of the interventions are just changing your environment one time and then you get an ongoing benefit,” he says. “There may be a greater upfront cost to some of the environmental interventions, but in the long term you’re better off doing that than taking medicine all the time and being sick.”

Portnoy’s final words of advice? “Pay attention to your environment. It makes a difference.”

Have a healthy home comment? Write to: [email protected]

Easy Ways to Defeat Your Dust Mite Allergy

Dust mites don’t bite but they can cause other problems.

What’s the grossest bug you can think of? Cockroach? Nope. Centipede? Nope. Spider? Well yes, but there’s a different one that we’re thinking of: the dust mite.

These things are ugly. They’re nasty and kind of look like something from out of a horror movie. They’re also everywhere, including your home, your carpet, your bed, and even your face.

Okay, we didn’t mean to scare you there. The dust mite may be everywhere, but it’s almost completely harmless and pretty normal to have around. The concern with dust mites doesn’t come from the bugs themselves. Dust mites cannot and do not bite. They are not parasites. The bugs themselves can’t do direct harm. The concern with these tiny little nasty looking things is the allergens they produce.

What is a dust mite?

A dust mite is a microscopic pest that kind of looks like an insect but is technically not one. They look a lot like a teeny tiny cockroach, and they don’t have a face, which makes them more or less ugly depending on what you think of bug faces. You can’t see a dust mite with the naked eye, as adult ones are only about five micrometers long. That’s about the size of your average bacterium.

Dust mites feed primarily on gross stuff like dander and skin cells, thus are frequently found in places where that stuff builds up like mattresses, couches, and linens. As most homes have these things, the vast majority of houses would have a detectable dust mite presence if tested.

Dust mites can be tested for by collecting some dust and looking at it under a microscope.

Where do dust mites live?

As stated, dust mites love fabrics and places where dead skin cells collect. They’re big fans of dander and flakes of skin and prefer to eat that. Mattresses are often their go-to hideout as humans probably shed more skin cells there than anywhere else. Carpets, couches and soft chairs, rugs, and curtains are also prime dust mite habitat.

Humidity is an essential factor in your home’s ability to house and breed dust mites. These creatures don’t drink water, but instead, absorb it from the air around them. Because of this, they can become dehydrated and die in environments where the humidity levels are too low.

Optimum conditions for growth and development are around 75-80 degrees F and 70-80 percent relative humidity. House dust mites absorb and lose moisture through their skin, and are very vulnerable to dehydration. Consequently, humidity levels within the home have a significant effect on survival. Dust mites cannot survive well at relative humidities below 50 percent. (Source: University of Kentucky Entomology Dept )

What are dust mite allergies?

Dust mite allergies are a little like pet allergies in the sense that it isn’t the creature itself that you are allergic to, but rather a protein that it releases. These proteins are released from the mites when they shed skin and expel waste.

These allergens build up on soft surfaces and can be sent in the air easily by the shaking out of sheets, lifting of couch cushions, or walking on carpets. Next thing you know, lots of allergens are populating your air.

Dust mite allergies also don’t have a particular season, so symptoms happen year round. This is unfortunate for the more than 25 million Americans who have asthma, as dust mite allergies are prevalent among asthmatics and are often identified as the root cause of its development.


  • Sneezing
  • Runny nose
  • Itchy eyes
  • Congestion
  • Cough
  • Can trigger an asthma attack

How do you treat dust mite allergies?

The most successful approach to treating dust mite allergies is to remove the things from your home that dust mites require to survive. This can be done with a couple of easy steps, which we’ll break down right here.

First, it’s essential to understand that you’re never getting rid of all dust mites. There is always going to be some dust mites lumbering about in your home. You can, however, significantly reduce the number of them and make your home much healthier with some simple and routine items.

Decrease the humidity

Humidity is a vital environmental element for dust mites. They need a high level of humidity to survive, so stripping them of that is an effective way to make your home environment non-conducive to dust mites.

A dehumidifier is the best way to do this. This home appliance does exactly what it sounds like: decrease the humidity. These devices work by pulling air into them like an air conditioner and then using a refrigerant to condense water vapor in the air into water droplets. The droplets then fall into a pan or reservoir that you empty when it’s full. Quite simply, it pulls the water out of your air.

Dehumidifiers come in a variety of sizes and a range of prices. The smallest is the portable kind, which works well for individual rooms like a bathroom or closet, and they start at only around $20. Larger dehumidifiers that work for entire areas of your home will cost into the hundreds, and whole-house models even exist that cost four digits.

High humidity in the home contributes to the presence of more allergens than just dust mites. Molds and other fungi love humid environments. So a dehumidifier is an excellent way to tackle multiple different allergens.

If you live in a southeastern state, where the air is made of soup during the summer, congratulations. You’re more vulnerable to dust mites in your home than most other places.

Remove carpeting if possible.

Another effective way to make your home a less appealing environment for dust mites is to remove as many soft surfaces as possible. Soft surfaces, like carpets, are predisposed to dust mites because of how well they hold pollutants like dust and skin cells. Removing carpets altogether seems extreme, and it may be in many cases. In severe allergy cases, though, it may be necessary.

Hardwood floors will still accumulate allergens and allergy attractors like dust and skin cells on them. They’re much easier to clean though, and particles don’t get stuck inside them.

If you elect to stick with carpet, be sure to get low-pile carpet. It is easier to clean and has less capacity for holding dust and particles. High-pile carpeting is pretty much an allergy-sufferers worst nightmare, so stay away from that.

Vacuum and dust often.

Routine cleaning of the surfaces in your home is an absolute must for dust mite allergy sufferers. Allergens that dust mites produce can settle quickly into dust and get suspended in the air with the dust particles. Dusting with a damp cloth or paper towel will help collect these allergens with the dust particles. You should dust at least once a week.

Regardless of whether you have carpet or hardwood, include weekly vacuuming with your weekly dusting. A vacuum designed to take on pet hair works well, as dander is often released with pet hair and is a primary attractor of dust mites. These vacuums typically come with a HEPA filter to trap small allergens like pet dander. A HEPA filter vacuum is critical for dust mite allergy sufferers because dust mite allergens are also quite small and could blow back into your home without said filter.

Wash mattresses and sheets even more often.

In addition to vacuuming and dusting your home’s surfaces, washing your bed sheets and covers at least once a week is an easy and effective countermeasure in the fight against dust mites. As mentioned above, mattresses and things on mattresses are spot number one for dust mites. You spend more time in your bed than any other place in your home, so naturally, this is where most of the dead skin will accumulate.

Humidity is naturally increased on your mattress because you perspire when you sleep, adding to the attractiveness of the mattress to the dust mite.

Wash your sheets, covers, and pillowcases at least once a week and make sure to wash in hot water. If hot water isn’t an option, you can opt for allergen-targeting laundry detergent. These detergents use an additive called ACARIL to specifically target allergens like dust mites and the things they eat.

It’s pretty important to clean your mattress regularly too, as washing your linens only tackles part of the problem. Baking soda is a pretty potent weapon against dust mites in your bed. Using it is a simple process as well. Add a little bit of essential oil to the baking soda and then spread it across the top of your mattress, then vacuum. This is a proven way to help rid your mattress of a dust mite infestation.

Use of essential oils can help to kill the dust mites before the vacuuming begins.

Use at least a MERV 8 pleated air filter.

While Allergens produced by dust mites may not stay suspended in the air as long as other allergens, they can still enter the air very easily. Sitting down on a couch, falling onto your bed, or lifting your sheets to make your bed can send dust mite droppings and other allergenic mite products into the air you breathe. This creates a situation ripe for an allergic reaction.

If you’re using a low-quality air filter, it might not catch these allergens, which allows them to cycle back into your home and the air you breath. Using a pleated air filter of at least a MERV 8 rating will help to eliminate dust mite allergens from your home that are floating in the air.

Take medication.

If you find that eliminating the environment for dust mites isn’t working as well as you’d like, over-the-counter allergy medications like antihistamines and decongestants can treat your symptoms. These are usually inexpensive and available at about any grocery store or general store.

Dust mites are pretty nasty, and the allergens they produce can be a real problem in your home. Luckily, with the right routine cleaning practices, you can make your home a much less appealing environment for these microscopic pests and much more appealing environment for you and your family.

Dust Mites: Is Resistance Futile?

Latest Allergies News

Decimating Dust Mites Doesn’t Stop Asthma, but Doctors Not Deterred

April 15, 2008 — You can fight dust mites, but you can’t win.

An analysis of clinical studies shows that even if you succeed in getting rid of most of the dust mites in your home, it won’t prevent allergic asthma triggered by the Lilliputian pests.

Peter C. Gotzsche, MD, DrMedSci, director of the Nordic Cochrane Center in Copenhagen, Denmark, and colleague H.K. Johansen, MD, DrMedSci, analyzed 54 clinical trials involving more than 3,000 asthma patients.

In each trial, researchers took on house dust mites with physical methods such as mite-proof mattress casings and vacuums, mite-killing chemicals, or a combination of physical and chemical methods to fight the mite.

«We were unable to demonstrate any clinical benefit to mite-sensitive patients with asthma,» Gotzsche and Johansen write. «We conclude that the trials of current chemical and physical methods aimed at reducing exposure to house dust mite allergens failed to find an effect.»

The finding may come as a surprise to people allergic to dust mites, many of whom have spent — and are spending — serious time, money, and effort in their battle against the bugs.

Dust Mites Small in Size, Great in Number

House dust mites fall into the category of things we’d rather not think about. They are as ugly as they are small. And they are very small. Ranging in size from a hundredth to a thousandth of an inch, they’re too small to see without magnification.

Like spiders, dust mites are eight-legged arachnids. The good news is they don’t bite. The bad news is they do eat the dried, dead skin that sloughs from our bodies every day. It’s a rich source of food, as we shed about a fifth of an ounce of skin a day. It makes up about 80% of the dust you see in an indoor sunbeam.

As many as 19,000 dust mites can be found in a ball of dust the weight of a 1 gram paper clip, although the typical dust ball contains only 100 to 500 mites. Contrary to popular belief, dust mites don’t live in your heating/air ducts. But they love living in your mattress and in your pillow, where your body provides them not only food but also the moisture and warmth they crave.

Hideous to behold under the microscope, dust mites themselves aren’t really a problem. But their shells, their feces, and their corpses break down into potent allergy-causing proteins or allergens. That’s why just killing dust mites isn’t enough. Dust-mite control means getting rid of dust-mite dust, and — because you can’t totally get rid of them — keeping dust-mite populations low.

Mite Resistance Not Futile, Allergists Say

Even though researchers were able to significantly reduce dust-mite allergens in several studies, Gotzsche and Johansen note that this did not help people’s asthma.

«The explanation that we find most plausible for the lack of effect of the interventions is, therefore, that the methods we have reviewed do not adequately reduce mite antigen levels,» they write. «Mite-sensitive asthmatic patients are usually sensitive to other allergens, so that successful elimination of only one allergen may have limited benefit, whatever its success.»

That last phrase is key, says allergist Leonard Bielory, MD, director of the asthma research center at UMDNJ-New Jersey Medical School, Newark.

«Getting rid of dust mites alone is not the answer,» Bielory tells WebMD. «When we discover that patients have dust-mite allergy, we tell them it is rarely just dust mites.»

Allergist Jonathan A. Bernstein, MD, of the University of Cincinnati, bristles at the suggestion that mite resistance is futile for allergic people.

«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,» Bernstein tells WebMD. «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.»

Over time, Bielory and Bernstein insist, 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.

How to Fight the Mite

It’s really not feasible to permanently rid your house of dust mites, says Greg Baumann, senior scientist for the National Pest Management Association.

«They are here to stay for sure,» Baumann tells WebMD. «The pest control industry really does not deal with dust mites because there are so few products out there professionals can use. They are very, very hard to control. You do not have any magic wand to wave.»

Entomologist Ron Harrison, PhD, director of training for the pest-control firm Orkin Inc., agrees with Baumann.

«You don’t want dust mites in your home, but there may not be techniques that are helpful,» Harrison tells WebMD. «We typically don’t target dust mites because they are so small and don’t fit under Orkin’s goals for eradication. But if people ask us to come in, we don’t shy away from saying, ‘Here are some things that might help.'»

Bernstein says acaricides — pesticides that target mites — aren’t particularly helpful in reducing dust-mite allergens. Baumann suggests this is because poison simply turns live mites into dead mites, which continue to cause allergies while dust mite populations rebound.

But all of the pest and allergy experts who spoke with WebMD agree that expensive efforts aren’t worth the cost.

«People don’t need to go out and spend an exorbitant amount of money to do a good intervention,» Bernstein says. «It is simply a matter of reasonably good hygiene and what you would do anyway. You would control humidity and vacuum and tidy up the room and not have a lot of dust-gathering collectibles and hang things up and put things in drawers.»


«Just taking better care of yourself takes care of your allergy,» Bielory says. «You keep yourself in a cleaner, healthier environment, and your allergy will improve.»

Each of the experts disagrees over details. Bernstein says that mite-proof mattress and pillow covers are a good idea. Bielory says these products make the bed uncomfortable and that poorer sleep is a factor that makes allergy worse. But here’s a list of what many experts say will — by and large — reduce your home exposure to dust-mite allergens:

  • Get white sheets and pillowcases for your bed and wash them every week in very hot water. Wash the mattress pads and blankets, too.
  • Vacuum regularly, but not within two hours of bedtime. A HEPA filter isn’t necessary and may not help. If you’re allergic to dust mites, wear a dust mask while vacuuming or get out of the house while someone else vacuums. Vacuums raise residual dust, and you should wait for it to settle.
  • Remove stuffed animals and dusty clutter from the bedroom.
  • Remove upholstered furniture from the bedroom and from other rooms in which you spend a lot of time.
  • Get a dehumidifier. Dust mites love humidity. Keeping humidity in the 30% to 50% range helps control dust mites.
  • Consider putting mite-blocking covers on your mattress and pillows.
  • Consider removing fabric window coverings and replacing them with plastic ones.
  • Get rid of tapestries or fabric wall hangings.
  • Consider replacing carpeting with tile or wooden floors.
  • Do not hire a duct-cleaning service. Dust mites do not live in working heating and air-conditioning ducts.
  • Clean the air filters on your furnace/air conditioner at least once a month.

Gotzsche and Johansen argue that these steps are not proven to help asthma.

«Reviews and guidelines do not reflect the fact that measures designed to reduce the patients’ exposure to mite antigen in the home are ineffective,» they write. «The recently published, very extensive [2007] U.S. guidelines for asthma control were also misleading . Reviews and guidelines should reflect the facts.»

But Bielory says patients should not give up.

«Patients need to be empowered — they can’t just take a pill and have their allergy go away,» he says. «If you clean your home, even if it is a placebo effect, it is something positive. People feel better because they are doing something.»

The Gotzsche review appears in the April 16 issue of Cochrane Database of Systematic Review.

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