Dust mite allergy
What is it?
- Dust mite allergy is an immune system reaction to a certain dust mite protein. This reaction triggers inflammation in the lining of the nasal passages (allergic rhinitis), causing sneezing, runny nose and other signs and symptoms associated with hay fever.
- For some people, dust mite allergy may be the primary cause of inflammation and contraction of airways of the lungs (asthma), resulting in wheezing, shortness of breath and other breathing difficulties.
- Dust mites, relatives of the spider, are too small to see without a microscope. Dust mites eat skin cells shed by people, and they thrive in warm, humid environments. In most homes, bedding, upholstered furniture and carpeting provide an ideal environment for dust mites.
- Steps to reduce the number of dust mites in your home can often control dust mite allergy. Medications or other treatments may be necessary to relieve symptoms and manage asthma.
Dust mite allergy symptoms caused by inflammation of nasal passages include:
- Runny nose
- Itchy, red or watery eyes
- Nasal congestion
- Itchy nose, roof of mouth or throat
- Postnasal drip
- Facial pressure and pain
- Frequent awakening
- Swollen, blue-colored skin under your eyes
- In a child, frequent upward rubbing of the nose
If your dust mite allergy contributes to asthma, you may also experience:
- Difficulty breathing
- Chest tightness or pain
- An audible whistling or wheezing sound when exhaling
- Trouble sleeping caused by shortness of breath, coughing or wheezing
- Bouts of coughing or wheezing that are worsened by a respiratory virus such as a cold or the flu
A dust mite allergy can range from mild to severe. A mild case of dust mite allergy may cause an occasional runny nose, watery eyes and sneezing. In severe cases, the condition is ongoing, or chronic, resulting in persistent sneezing, cough, congestion, facial pressure or severe asthma attack.
Dust mites eat skin cells people shed, and rather than drinking water, they absorb water from humidity in the atmosphere. They thrive in temperatures around 70 F (21 C) and a relative humidity around 70 percent.
Household dust contains all kinds of tiny particles, but a large portion of it is made up of human skin cells. This dust is easily trapped in the fibers of bed linens, furniture cushions and carpeting. These materials also hold moisture well. Consequently, bedrooms are ideal habitats for dust mites.
Dust also contains the feces and decaying bodies of dust mites, and it's a protein present in this dust mite "debris" that's the culprit in dust mite allergy.
What causes the allergic reaction
An allergic reaction is somewhat like a case of mistaken identity within your body's immune system. Normally, your immune system generates antibodies to protect your body against bacteria, viruses or toxic substances.
If you have dust mite allergy, your body generates an allergy-causing antibody to a protein found in the dust mite debris. In other words, it's mistakenly identified this protein as something that could harm you. Once your body has developed an allergy-causing antibody to a particular agent (allergen) — in this case, the dust mite protein — your immune system will be sensitive to it. When you inhale dust mite debris, your immune system responds and produces an inflammatory response in your nasal passages or lungs.
The dust mite allergen can cause two kinds of immune system responses in the airways of your lungs. An allergen can prompt inflammation in air passages. Therefore, prolonged or regular exposure to the allergen can cause the ongoing (chronic) inflammation associated with asthma. Exposure to an allergen also may cause sudden, severe constriction of air passages (bronchospasms).
The following factors increase your risk of developing a dust mite allergy:
- Family history. You're more likely to develop a sensitivity to dust mites if allergies run in your family.
- Exposure. Being exposed to high levels of dust mites, especially early in life, increases your risk.
- Age. You're more likely to develop dust mite allergy during childhood or early adulthood.
Ongoing (chronic) inflammation of tissues in the nasal passages caused by dust mite allergy can obstruct your sinuses, the hollow cavities connected to your nasal passages. These obstructions may make you more likely to develop infections of the sinuses (sinusitis).
People with asthma and dust mite allergy often have difficulty managing asthma symptoms. They may be at risk of asthma attacks that require immediate medical treatment or emergency care.
Your doctor may suspect dust mite allergy based on symptoms, an examination of your nose and your answers to his or her questions.
He or she may use a lighted, instrument to look at the condition of the lining of your nose. If you have an allergy to something airborne, the lining of the nasal passage will be swollen and may appear pale or bluish.
Your doctor may suspect a dust mite allergy, based on your comments. For example, if your symptoms are worse when you go to bed or while cleaning — when dust mite allergens would be temporarily airborne — you may have dust mite allergy.
If you have a pet — another common source of allergies — it may be more difficult to determine the cause of the allergy, particularly if your pet sleeps in your bedroom. The source of your allergy may be clearer after you take steps to reduce levels of the possible allergens from your home.
Allergy skin test
Your doctor may suggest an allergy skin test to determine exactly what you're allergic to. You may be referred to an allergy specialist (allergist) for this test.
In this test, tiny drops of purified allergen extracts — including an extract for dust mites — are pricked onto your skin's surface. This is usually carried out on the forearm, but it may be done on the upper back.
The drops are left on your skin for 15 minutes before your doctor or nurse observes your skin for signs of allergic reactions. If you're allergic to dust mites, you'll develop a red, itchy bump where the dust mite extract was pricked onto your skin. The most common side effect of these skin tests is itching and redness. This usually goes away within 30 minutes.
In some cases a skin test can't be performed because of the presence of a skin condition or because of interactions with certain medications. As an alternative, your doctor may order a blood test that screens for specific allergy-causing antibodies to various common allergens, including dust mites. This test may also indicate how sensitive you are to an allergen.
Treatments and drugs
The first treatment for controlling dust mite allergy is avoiding dust mites as much as possible. When you minimize your exposure to dust mites, you should expect to have allergic reactions that are less often or less severe. However, it's impossible to completely eliminate dust mites from your environment. You may also need medications to control symptoms.
Your doctor may direct you to take one of the following medications to improve nasal allergy symptoms:
- Antihistamines reduce the production of an immune system chemical that is active in an allergic reaction. These drugs relieve itching, sneezing and runny nose. Prescription antihistamine tablets include fexofenadine and desloratadine. Azelastine and olopatadine are prescription antihistamines taken as a nasal spray. Over-the-counter antihistamine tablets (Claritin), as well as antihistamine syrups for children, also are available.
- Corticosteroids delivered as a nasal spray can reduce inflammation and control symptoms of hay fever. These drugs include fluticasone (Flonase), mometasone furoate (Nasonex), triamcinolone (Nasacort). Nasal corticosteroids provide a low dose of the drug and have a much lower risk of side effects compared with oral corticosteroids.
- Decongestants can help shrink swollen tissues in your nasal passages and make it easier to breathe through your nose. Some over-the-counter allergy tablets combine an antihistamine with a decongestant. Oral decongestants can increase blood pressure and shouldn't be taken if you have severe high blood pressure or cardiovascular disease. In men with an enlarged prostate, the drug can worsen the condition. Talk to your doctor about whether you can safely take a decongestant. Over-the-counter decongestants taken as a nasal spray may briefly reduce allergy symptoms. If you use a decongestant spray for more than three days in a row, it can contribute to congestion.
- Cromolyn sodium prevents the release of an immune system chemical and may reduce symptoms. You need to use this over-the-counter nasal spray several times a day, and it's most effective when used before signs and symptoms develop. Cromolyn sodium doesn't have serious side effects.
- Leukotriene modifiers block the action of certain immune system chemicals. Your doctor may prescribe this prescription tablet, montelukast (Singulair). Possible side effects include headache. Less common side effects include abdominal pain, cough, dental pain and dizziness.
- Immunotherapy, a series of allergy shots, can "train" your immune system not to be sensitive to an allergen. One to two weekly shots expose you to very small doses of the allergen, in this case, the dust mite protein that causes an allergic reaction. The dose is gradually increased, usually during a three- to six-month period. Maintenance shots are needed every two to four weeks for three to five years. Immunotherapy is usually used when other simple treatments don't work well.
- Nasal lavage is the use of a saltwater (saline) rinse for your nasal passages. Your doctor may suggest a saline rinse to help lessen congestion, sneezing and postnasal drip. You can purchase over-the-counter saline sprays or nasal lavage kits with devices, such as squeeze bottles, to administer a rinse. You can make your own solution with 1/8 teaspoon (5 milliliters) of table salt in 8 ounces (237 milliliters) of distilled or purified water. Mix the ingredients together and store the solution at room temperature, and remix another batch after a week. Lavage your nose daily.
Avoiding exposure to dust mites is the best strategy for controlling dust mite allergy. While you can't completely eliminate dust mites from your home, you can significantly reduce their number. Use these suggestions:
- Use allergen-proof bed covers. Cover your mattress and pillows in dust-proof or allergen-blocking covers. These covers, made of tightly woven fabric, prevent dust mites from colonizing or escaping from the mattress or pillows. Encase box springs in allergen-proof covers.
- Wash bedding weekly. Wash all sheets, blankets, pillowcases and bedcovers in hot water that is at least 130 F (54.4 C) to kill dust mites and remove allergens. If bedding can't be washed hot, put the items in the drier for at least 20 minutes at a temperature above 130 F (54.4 C) to kill the mites. Then wash and dry the bedding to remove allergens. Freezing nonwashable items for 24 hours also can kill dust mites, but this won't remove the allergens.
- Keep humidity low. Maintain a relative humidity between 30 and 50 percent in your home. A dehumidifier or air conditioner can help keep humidity low, and a hygrometer (available at hardware stores) can measure humidity levels.
- Choose bedding wisely. Avoid bedcovers that trap dust easily and are difficult to clean frequently.
- Buy washable stuffed toys. Wash them often in hot water and dry thoroughly. Also, keep stuffed toys off beds.
- Remove dust. Use a damp or oiled mop or rag rather than dry materials to clean up dust. This prevents dust from becoming airborne and resettling.
- Vacuum regularly. Vacuuming carpeting and upholstered furniture removes surface dust — but vacuuming isn't effective at removing most dust mites and dust mite allergens. Use a vacuum cleaner with a double-layered microfilter bag or a high-efficiency particulate air (HEPA) filter to help decrease house-dust emissions from the cleaner. If your allergies are severe, leave the area being vacuumed while someone else does the dirty work. Stay out of the vacuumed room for 20 minutes after vacuuming.
- Cut clutter. If it collects dust, it also collects dust mites. Remove knickknacks, tabletop ornaments, books, magazines and newspapers from your bedroom.
- Remove carpeting and other dust mite habitats. Carpeting provides a comfortable habitat for dust mites. This is especially true if carpeting is over concrete, which holds moisture easily and provides a humid environment for mites. If possible, replace wall-to-wall bedroom carpeting with tile, wood, linoleum or vinyl flooring. Consider replacing other dust-collecting furnishings in bedrooms, such upholstered furniture, nonwashable curtains and horizontal blinds.
Air purifiers collect airborne dust in your home and can help with controlling dust if you also maintain vigorous cleaning practices. But purifiers won't remove dust mites because the mites are too heavy to remain airborne long enough to be filtered through an air purifier. Some dust mites may be airborne right after cleaning, but they quickly settle again onto surfaces.