Asthma and dust mites

By John Leung, MD


One in five Asian immigrant children has asthma. In allergic asthmatics, effective avoidance of allergens can improve symptoms and may reduce the use of medications. The first step is to identify the specific allergens that trigger one’s asthma symptoms. This is usually done by blood testing or skin testing performed by a certified allergist.

Major indoor allergens include dust mites, cats, dogs and cockroaches. Today, we will discuss how to avoid dust mites effectively in allergic individuals. Dust mites are arthropods.

A dust mite. (Image courtesy of Flickr user arkhangellohim.)

A dust mite. (Image courtesy of Flickr user arkhangellohim.)

They look scary but they do not bite. They are very small and you cannot see them with the naked eye. They feed on moisture from the air and shed human skin. They live in pillows, mattresses, box springs, comforters and any woven materials, where there is plenty of food (shed human skin). It is their feces that cause the allergic reaction. Their feces are relatively heavy and normally are not airborne, thus air purifier is not helpful in removing them.

Here are some tips for effective dust mite avoidance:

1) Encase pillows, comforters and mattresses with special dust-mite proof covers. Regular bedding covers do not work because their large pore sizes allows free passage of dust mites.

2) Wash sheets, pillowcases, mattress pads and blankets weekly in hot water with detergent, and dry them in an electric dryer on a hot setting, to kill the dust mites.

3) Minimize the number of stuffed toys in your children’s bedrooms. They are havens for dust mites.

4) Decrease humidity by opening windows in a dry climate, or air conditioning in a humid climate. Dust mites feed on moisture and they cannot survive a dry environment.

5) Remove carpets or rugs from the bedroom if possible. If not, vacuum at least weekly using a vacuum equipped with a high-efficiency particulate air (HEPA) filter.

6) Replace upholstered furniture and drapes.

Don’t expect immediate results. It takes at least three to six months to see gradual improvement of symptoms. Remember, dust mite avoidance only works in asthmatics who are allergic to dust mites. Not all asthmatics are allergic to dust mites, and other allergens can also trigger asthma. Work with your allergist to find out what specific allergens are triggering your asthma. Asthma is a complex disease and allergen avoidance is only one of the four components in fighting asthma. Other key components include medications, patient education and routine monitoring by your doctor. Stay tuned, we will discuss these topics in upcoming issues.

If you have any questions about asthma, you can email Dr. Leung at


Dr. John Leung is triple-board certified in internal medicine, allergy/immunology and gastroenterology. He is the Director of the Food Allergy Center at Tufts Medical Center.

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