Dealing with dust mites

Every once in a while, scientists come up with a suggestion for leading a healthier life that we can all appreciate–unlike all those restrictive recommendations we get most of the time.

This week’s I-can-get-behind-that suggestion comes from a team of U.K. scientists researching dust mites, who recently announced that sleeping in and leaving the bed messy can help reduce dust mite infestation in bedrooms, thus providing teens everywhere with scientific arguments to use in their running bed-related battles with their parents.

The dust mite is a tiny, translucent, eyeless, eight-legged creature, measuring just 0.2 to 0.3 mm in length–smaller than the period in a newspaper, and thus pretty much invisible.

Dust mites can eat a number of things, but the primary component of their diet is shed animal skin cells. Since the average human sheds between five to 10 grams of dead skin every week, there’s lots to eat in the average home. (When you see motes of dust floating in a sunbeam in your house, about 80 percent of the visible material is human skin.)

Where dust mites live, house dust is often heavily contaminated with their fecal pellets and skins, a powerful allergen for some people, and something that can exacerbate asthma. Reducing the dust-mite population is therefore an urgent matter in many homes.

Beds are favorite mite-hangouts. A typical used mattress may have anywhere from 100,000 to 10 million living and dead mites inside, and according to one oft-quoted statistic, as much as one-tenth of the weight of a two-year-old pillow may be composed of dead mites and their droppings.

Suggestions to reduce mite infestations in beds include replacing feather and down pillows with pillows with synthetic stuffing; enclosing the mattress with a plastic cover and damp-dusting it daily; regularly and thoroughly vacuuming the mattress, pillows, and the base of the bed and changing and washing bedding weekly, frequently in very hot water (55 C or above). Ripping out the carpet and replacing it with wood, tile, linoleum or vinyl can also help.

There are insecticides that can kill dust mites, but the mites adapt quickly, and people generally look askance at spraying insecticide on their bed. However, dust mites do have an Achilles’ Heel that can be exploited: they need a fairly high relative humidity to thrive.

Mites don’t drink. Instead, they secrete a salt solution from the upper part of their front legs. As this solution makes its way to the mouth, it takes up water from the air. If the room gets too dry–below 50 percent relative humidity–the salt solution crystallizes, the mechanism shuts down, and the mites dehydrate.

That’s not to say that low humidity automatically kills all mites: they can survive in a dry, heated home even in the winter by clumping together into a “super-organism” that restricts the loss of water and might even allow them to absorb it at a lower relative humidity than otherwise. However, low humidity definitely limits their numbers.

That’s good news for us in Saskatchewan, because it means mites aren’t as much of a problem as they are in moister places–places like the U.K., which is why researchers there are studying how drying out the home environment could help people control dust mites.

They constructed a dust-mite “racetrack,” to see how mites move and are affected by changes in temperature and humidity. One end of the track was warmed with hot water, the other cooled. Placed on the track, the mites raced from the hot, dry end toward the cooler, more humid end.

In follow-up research now underway, the scientists are putting “mite pockets” and sensors to record the temperature and humidity in beds in 36 houses. They’ve already discovered that a single mattress can sustain up to 1.5 million mites in the right conditions.

So why are they recommending sleeping in and not making the bed? It turns out staying in bed longer raises the temperature of the mattress enough to make mites uncomfortable, causing them to migrate, even though they would ordinarily like the extra moisture produced by a sleeping body. You can achieve the same effect by raising the temperature of the bedroom.

Leaving the bedcovers off during the day, meanwhile, allows the sheets and mattress to dry out, forcing the mites to move to find water. Since even the steam from a shower can raise the humidity in a home enough to give mites their necessary daily drink, the researchers also suggest using fans or opening a window to let shower steam escape.

Or, hey, maybe you could stop taking showers altogether. Apparently, even dust mites don’t like a slob!

Permanent link to this article: https://edwardwillett.com/2004/11/dealing-with-dust-mites/

2 comments

    • Cassondra Jones on November 15, 2019 at 11:12 am
    • Reply

    Will spreading salt on shelves and floors dehydrate mites? I have a floor model clothes steamer and hair dryer. Will hot steam followed by hot hair dryer kill dust mites?? Tks

      • on November 18, 2019 at 9:24 am
      • Reply

      Not an expert, I’m afraid. Everything I know on the subject is in the column above, and I wrote it a LONG time ago.

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