Dust Mites in Your House
by Building Inspector and Indoor Air Specialist, Dan Schilling
© Copyright 2002 Residential Inspections LLC, All Rights Reserved
Dust mites are eight legged creatures from the spider family. They are microscopic and invisible to the naked eye. In fact, we should probably be glad that we cannot see them. I think if we could see them, most of us would move back outdoors.
Dust mites are part of the natural food chain. They clean up all the other stuff we cannot see. In a way, they make our world healthier for us to live in. The concern about dust mites surrounds the fact that we live with far too many of them indoors.
There are 15 different species of mites that have been found living with us in our homes. Just one ounce of common house dust can host as many as 42,000 dust mites. Approximately 10 million dust mites live in a bed; 8 million in a mattress and 2 million in a pillow. We never sleep alone.
Dust mites are essentially crawling stomachs and digestive systems. Their primary food source is dead skin shed from humans which accounts for approximately 80% of the dust in a home. They also eat fungus that grows on rotting dead skin.
Dust mite populations thrive in indoor environments. They live inside of carpeting, furniture, and especially inside of mattresses, bedding and pillows. One female can lay up to 100 eggs and mating begins within 24 hours after emergence of adults.
An entire dust mite population can reproduce itself in just 25 days, leaving the dead mites and skeletal remains from the former population behind. These dead mites and skeletal particles can accumulate and pose a concern of their own. The skeletons contain a protein that is also allergenic to humans and pets. Perhaps you have never thought about it before, but if you have an old pillow, you might notice how it is heavier than it was when it was new. Approximately 10% of the weight of a 5 year old pillow can be a blend of skeletal remains, live mites, the dead skin cells they feed on, and their fecal pellets. I have heard of some older pillows that have had as much as 50% of their weight consist of these particles.
If you could see on a microscopic level, it would look like a snow blizzard around your head area where you sleep. While perhaps not the only cause, these particles can cause snoring problems and breathing difficulties when sleeping. I have worked with people who could not sleep in their beds without the use of inhalers several times throughout the evening. These airborne particles can also cause people to feel fatigued, even after sleeping all night. Adults and children can wake up feeling cranky and sometimes with headaches. Children can have a hard time studying in school after breathing these particles all night long. Many children are stigmatized with ADD or dyslexia when they may simply be carrying a load of these particles in their sinus' throughout the day. Adults can also be affected by this phenomenon at while at work.
Perhaps the worst aspect of dust mite populations is their excrement. Mite feces is one of the most toxic allergens to humans and pets. Each single dust mite can excrete as many as 20 fecal pellets every day. When you have millions, well...you do the math!
Dust mites and their feces can become airborne simply from walking across carpet, sitting on furniture cushions, climbing into bed or moving a pillow while sleeping.
Inhaled fecal matter can lead to eye-ear-nose-throat infections, headaches, fatigue, depression, sleep difficulties, snoring and respiratory illnesses such as sinusitis, allergies and asthma attacks.
First understand that dust mites cannot be completely eliminated from indoor environments. It is possible to effectively control their numbers. Here's how:
Consistent vacuuming of carpeting, furniture and mattresses is essential to remove mites, mite feces, skeletal remains and dead skin. It is critical that a quality vacuum cleaner be used. Simply using better quality bags is not enough. The bags may trap the mites themselves, but can allow the much smaller fecal pellets to be thrown out into the air you breathe while you are vacuuming. Your vacuum cleaner should have a finishing filter that is HEPA quality (High Efficiency Particulate Air). These filters usually follow the bags to trap the micro-fine particles that pass through bags and keep them out of the air you are breathing.
Regular washing of bedding and pillow cases is also essential for the control of mites. I am amazed that people will use a clean towel to wipe off a clean body after bathing, and then throw it right in the laundry, yet, those same people will go to bed and wipe their bodies on sheets and pillow cases for eight hours at a time, night after night . Keep your bedding clean. Also, do not attempt to kill mites during laundering by turning up your water heater temperature. This can prematurely defect your water heater, waste fuel, and possibly cause someone to be scalded. Frequency of washing is a better plan.
Vacuuming mattresses on occasion can help. In some countries, people beat their mattresses outdoors to rid them of dust. When is the last time you did that? Vacuuming will accomplish the same goal, only much easier. As mentioned above, use a quality vacuum cleaner and use the furniture attachment. Go slowly across the surface to allow the vacuum to pull debris up and out of the mattress.
Pillow and Mattress Casings
I believe everyone should be making use of dust mite proof pillow covers on their pillows. Put one of these on before putting your regular pillow case on. If an individual already has breathing difficulties, dust mite proof mattress covers should also be used. When used underneath bedding and pillow cases, these covers provide a barrier to keep dead skin and mites out of the mattresses and pillows we sleep on. If you will be purchasing dust mite proof covers, buy the better quality covers and avoid the pillow covers made with slippery fabric to prevent your regular pillow cases from sliding off easily through the night. If you have an older pillow, have it cleaned and sanitized before encasing it, or toss it, and begin with a new one.
Control Indoor Humidity
Control of indoor humidity is important to control dust mites. Mites not only require food, but they need moisture to survive as well. Invest in a humidity gauge and monitor the humidity in your home. Do not allow the humidity level to rise above 50%. If necessary, use a dehumidifier. Most homes will need these during the spring, summer and fall months, particularly in areas below grade, such as finished basements. Some newer homes may need to run a dehumidifier during the winter months as well. A new home can have as many as forty tons of water moisture in the concrete and other building materials which make take a few years to dry out.
Unmake Your Bed
Men particularly like this solution. Instead of making your bed in the morning, unmake it! Why? OK, bare with me here as I explain. Human beings are essentially walking humidifiers. Every time you exhale, you emit 100% humidity. (You exhale approximately 22,000 times a day.) To further compound the bedroom moisture problem, we evaporate 100% humidity directly out of our skin. If I were to take a thermal hygrometer and place it next to your skin, it would register 100% humidity. The air under your bed covers will accelerate to nearly 100% humidity in as little as two minutes after going to bed. Through the night, this moisture penetrates deep into mattresses and pillows. When you make your bed in the morning, you are sealing up the dust mite restaurant. Your mites have just been given all the food and water they could ask for. This allows them to thrive, breed and lay eggs all day long. The solution is a simple one; dry out your bed everyday. Fold your covers back to the foot of the bed, exposing the undersides and the mattress. You might also want to place your pillow on edge to allow both sides to dry out during the day.
Sanitize Your Bedding
Many people are purchasing home air purification systems that replace essential, natural levels of activated oxygen (ozone) missing from indoor air. Some of these systems have the ability to produce higher levels of activated oxygen for sanitizing purposes. When used in the sanitizing mode, these machines can help to oxidize fecal pellets, body parts and the dead skin cells shed from humans and pets. The sanitizing setting is designed for use in temporarily unoccupied spaces, such as a bedroom might be during the day. If you have one of these systems, follow your sanitizing instructions. (See the two articles on ozone and air purifiers.)
Replace Your Ions
Air purifiers that replace natural, outdoor levels of electrical ions to your indoor air can be effective for removal of the airborne dust mites, fecal pellets, body parts and dead skin from the air. Replacing your ions will help settle these particles from the air where they can be cleaned, vacuumed, or drawn into an air vent and trapped in a furnace filter. Either way, they help to keep these particles out of your respiratory system. (See the two articles on electrical ions and air purifiers.)
Use Good Filtration
High efficiency furnace filters can help trap airborne mites, feces and dead skin. I recommend using washable electrostatic filters, pleated disposable filters, or the large cartridge type filters. There are various advantages to all three. (See the article about furnace filters.)
HEPA filters are also helpful but have a few disadvantages. They are suited for use in only one room per machine, the filter cartridges are relatively expensive to replace, and they can be a little loud when operating. Nonetheless, they are efficient at trapping these airborne particles and can help in bedrooms, especially if you do not have a forced air ventilating system.
By the way, the use of ionizers will increase the efficiency of both furnace and HEPA filters.
All in all, these are all relatively easy steps that you can take to protect yourself from the health affects of excessive mite contamination.
with those you care about.