Dust Mite Allergy

h-smile3What are house dust and dust mites?

House dust is a mixture of inert and allergenic substances. It may contain fibers from different types of household fabrics, bacteria, mold and fungus spores, food particles, human dander, bits of plants and insects, and other substances peculiar to an individual home, such as hair and dander from pets. Of these, mold and fungus spores, animal hair and dander, and house dust mites seem to be important allergens. The inert debris, while not including allergic symptoms, can nonetheless produce irritation.

House dust mites are microscopic relatives of spiders. They cannot be seen with the naked eye. Mites were identified in house dust as early as 1694. Only in recent years has their importance in human allergic reactions been clarified. Two species of mite, Dermatophagoides farina and Dermatophagoides pteronyssinus, are especially important. They enjoy warm and humid conditions, and would not be expected to be found in dry regions of the country. Both live and dead mites can cause allergic reactions. Although microscopic in size, dust mite particles contain large quantities of allergen. These particles, although heavier than pollen grains, are just the right size to enter the human respiratory tract. Dust mites live in areas of the home where people are. They might be found in a favorite upholstered couch or easy chair, but are particularly fond of pillows and mattresses, as well as in carpets around these items of furniture. Pillows themselves don’t cause allergic symptoms – it’s the dust mites and their particles contained in the pillows! Dust mites are not known to be carries of human disease, and do not cause infection. They do not bite or cause skin rashes, and in and of themselves are not dangerous.

Dust mite allergy is not necessarily a sign of a dirty home. Getting rid of dust mites is not currently possible and is complicated by the fact that usual cleaning methods like vacuuming, dusting and sweeping temporarily increase levels of dust mite particles in the air. They resist vacuuming because they burrow deep in carpet fibers.

What are the effects of a dust mite allergy?

Allergy to house dust mites may produce symptoms of sneezing, runny or stuffy nose, and watery, itchy eyes. These symptoms, often called allergic rhinitis, are similar to those produced by seasonal allergy to pollen, or hay fever. House dust mites can trigger allergic asthma, a noncontagious condition of the lungs characterized by episodes of narrowing of the bronchial airways. This constriction brings on wheezing, coughing, and shortness of breath characteristic of an asthma attack. Allergy is a very important trigger of asthma symptoms in many patients. Because house dust mites are so widespread, allergic symptoms from dust mite exposure does not usually vary from season to season. In fact, allergy to dust mites is probably the most common cause of allergic rhinitis occurring the year round.

How is a dust mite allergy detected?

Dust mite allergy is easy to diagnose. After a careful allergy history and relevant physical examination, allergy tests can be done using extracts from the two major dust mites. Results of this type of testing are available within 15 minutes of skin test application. Positive skin tests mean that the patient is allergic to the house dust mite. Occasionally, when skin testing is impossible, a less sensitive allergy blood test is used.

How is a dust mite allergy treated?

There is no permanent cure for any of the diseases associated with allergy, nor is there any permanent cure for the allergy itself. There are four ways to deal with the symptoms of dust mite allergy. First, when symptoms are mild and not particularly troublesome, they may be ignored.


The most straightforward treatment for dust mite allergy is to avoid or minimize exposure to the allergen. Complete avoidance of dust is not possible, but a careful implementation and maintained anti-dust program in the home should reduce symptoms significantly. Our recommended dust mite avoidance measures are listed at the bottom of this page. This program should be given a trial of four to six weeks before it is considered a failure.


Another aspect of treatment includes use of medications recommended or prescribed by the physician. These generally act in one of three ways: to block the release of the chemical mediators of allergy symptoms; to reduce the inflammation caused by the mediators; or to block the effects of histamine, one of the major mediators of nasal allergy symptoms.

  • Cromolyn sodium (Intal, Opticrom, Nasalcrom) is a medication that blocks the release of chemical mediators. It works in asthma, allergic rhinitis, and allergic conjunctivitis, although not in all patients. It must be used at least four times daily, and works better as a preventative agent if started before the onset of symptoms.

  • Corticosteroids counteract the inflammation caused by release of mediators, as well as that caused by other non-allergic factors. Sometimes corticosteroids are injected or taken orally, but usually on a short-term basis for extremely severe symptoms. Injected or oral steroids may produce severe side effects when used for long periods or used repeatedly. In asthma or rhinitis, corticosteroids are much safer when used topically by inhaling it into the lungs or spraying it on the mucous membrane of the nose.

  • Antihistamines are the most inexpensive and the most commonly used treatment for allergic symptoms. There are many different antihistamines, and there are wide variations in house individual patients respond to them. For this reason, there are many preparations available over the counter and by prescription. Generally, they work well, and produce only minor side effects, if any.

Other medications used in treatment allergy symptoms include sympathomimetic and anticholinergic drugs. Decongestant nose sprays and oral decongestants are in the sympathomimetic drug group. Temporary use of decongestant nose sprays is useful when nasal congestion is unbearable, but these over-the-counter drugs should not be used for more than four or five days at a time without a physician’s order, because they can produce a “rebound effect”. In other words, symptoms are at first relieved, but eventually become worse because of the medication itself. Oral decongestants do not produce this effect, but should be used only under a physician’s supervision in patients with high blood pressure. Often, an antihistamine is combined with a decongestant. Anticholinergic drugs are sometimes used to relieve symptoms of allergy; in fact, most antihistamines have a slight anticholinergic effect.

Allergy Shots (Immunotherapy or Desensitization)

One or more of the above medications, accompanied by an anti-dust program, will usually control most symptoms. If not, allergen injections (allergy shots, immunotherapy, desensitization) may provide additional relief. The treatment program consists of injections of a diluted extract, administered frequently in increasing does until a maintenance dose is reached. Then, the injection schedule is changed so that the same dose is given with longer intervals between injections. Immunotherapy helps the body build resistance to the effects of the allergen, reduces the intensity of symptoms provoked by allergen exposure, and sometimes can actually make skin test reactions disappear. As resistance develops, symptoms should improve, but the improvement from immunotherapy will take several months to occur. Desensitization is not a substitute for dust mite control measures.

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