Mites – A leading trigger for asthma and allegies

House dust mites and their droppings are one of the most significant asthma and allergy triggers. House dust mites, or more specifically their airborne feces, are a potentially serious allergen. Their basic food source is skin flakes - dander - which makes up about 80% of household lint. However, mites cannot feed or develop on "raw" dander. Dander must be defatted and partially digested by an aspergillus fungus.

The growth of the fungus requires fairly high humidity to grow. Further, at humidity levels much below 70% the mites tend to lose more moisture than they can acquire, which ultimately is lethal to the mite. It is generally considered that 60% relative humidity is the absolute minimum where dust mites can occur.

Special Note for Colorado and other low humidity states.

Given that relative humidity in Colorado averages about 35% (and considerably lower in homes during winter) dust mites are not a concern.

Dr. Nelson of National Jewish Hospital in Denver did a survey of house dust mites in Colorado several years ago. He found none, with one exception. The exception was an invalid, confined to bed with a humidifier running constantly next to the bed. Dr. Nelson concluded that dust mites are not a problem in the state.

Yes, but what should we actually do to get rid of mites and their dust?

Different sources will give you surprisingly different advice. Some of the differences are due to our uncertainties and a genuine difference of opinion between experts. Below is a list of some ways to address the dust mite issue. Much of this advice is not scientific, merely “tried and true” practices in the home. As always, make sure that you or your patient have been tested for dust mite allergies before working to rid your home of dust mites.

The two best ways to reduce the impact of dust mites in your home are:

Control Humidity
If your home has a humidity controlled environment, it is very difficult for dust mites to live (and therefore irritate). See the section "Humidity At Home" to learn how to keep the humidity in your home between 35% to 55%.

Clean The Air
Controlling the dust in your home will also help to reduce the effects of dust mites. HEPA vacuum cleaners and air cleaners are the best strategies for controlling dust and particles in your air. (See both these sections HEPA Vacuums and Air Cleaners)

Some Other Tips

• Use dust-proof bedding covers. It is essential to cover mattresses, pillows and duvets (comforters). Ideally, get a new bed or at least mattress, pillow and duvet and cover these with special covers before they are ever used. Then they will not merely stop dust moving from mattress to lungs, but will prevent harmful dust buildup in the first place.

• Vacuum (see HEPA Vacuum Cleaners in this section) or wipe dust-proof bedding covers regularly, that is, follow the manufacturer's instructions. Wash according to manufacturer's instructions.

• Launder other bedclothes (sheets, pillowcases, bedspreads) at 140 degrees F (HOT). Lower temperatures do not kill mites. Many bedclothes will not stand up to this temperature, so choose bedclothes that will.

• Where feasible, preferred flooring is hardwood or tile. Carpet tends to harbor duct, mold and dust mites.

• Do not give furry toys to children to take to bed. An excellent substitute is a cotton blanket which can be washed regularly at 140 degrees F or higher.

• Many people recommend putting furry toys into the freezer for 24 hours to kill any mites.

• Mite dust takes about two hours to settle from the air onto surfaces in an undisturbed room. Airing a room by opening windows is probably faster. But draughts may raise dust from the floor into the air.

• Damp-dust instead of vacuuming if you do not have a HEPA vacuum cleaner, but dampen the cloth as little as is necessary to stop the dust from flying about; very little dampness is needed.

• Replace soft cloth-upholstered furniture with dust-proof furniture. In practice, this means wood, plastic or leather furniture. 

• Take dust-proof bedding covers with you when you travel. Spare beds in other homes are likely to be a real problem. Hotel beds vary; likely to be better the more expensive the hotel in my experience, but this is not completely predictable. Wash the covers when you get home.

• Rarely used sleeping bags can be terrible. Dry clean immediately on return from each journey, then store in plastic bag without holes. For the cost of dry cleaning you could almost get a new cheap sleeping bag. But this does work.

• If you must do the vacuuming and bedmaking and you yourself are the sufferer, wearing a good filter breathing mask will help. Get them from any pharmacy or home improvement store.