Allergy Types: Other Allergies: Dust Allergy
Dust mite allergy is an allergic reaction to tiny bugs that commonly live in house dust. Signs of dust mite allergy include sneezing and runny nose. Many people with dust mite allergy also experience signs of asthma, such as wheezing and difficulty breathing.
Dust mites, close relatives of ticks and spiders, 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 mites eat skin cells people have shed, and rather than drinking water, they absorb water from humidity in the atmosphere. They thrive in temperatures between 65 and 84 F (18.5 and 29 C) and a relative humidity higher than 50 percent.
House 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 the proteins present in this dust mite “debris” that are the culprit in dust mite allergy.
What causes the allergic reaction
Allergies occur when your immune system reacts to a foreign substance such as pollen, pet dander or dust mites.
Your immune system produces proteins known as antibodies. Some of these antibodies protect you from unwanted invaders that could make you sick or cause an infection. When you have allergies, your immune system makes antibodies that identify your particular allergen as something harmful, even though it isn’t. When you inhale the allergen or come into contact with it, your immune system responds and produces an inflammatory response in your nasal passages or lungs. Prolonged or regular exposure to the allergen can cause the ongoing (chronic) inflammation associated with asthma.
The following factors increase your risk of developing a dust mite allergy:
- Having a family history of allergies. You’re more likely to develop a sensitivity to dust mites if allergies are more common in your family.
- Exposure to dust mites. Being exposed to high levels of dust mites, especially early in life, increases your risk.
- Being a child or a young adult. You’re more likely to develop dust mite allergy during childhood or early adulthood.
Skin prick or laboratory tests can help to confirm the clinical diagnosis in allergy. However, these tests are of limited value without a detailed clinical history. Skin prick tests are cheap and easy to perform once staff are trained, whereas serum (blood) IgE tests are more costly but still relatively cheap.’
Skin prick testing has been used successfully by doctors for over 130 years and the results are almost immediate. It is described as a safe, slight pin-prick delivery of an allergen or allergens just under the skin, usually on the arm. It is used to test and measure the sensitivity, of IgE driven histamine reactivity to foreign elements that may have found their way into the body. Most of these elements are proteins such as from cats, dogs or house dust mites. It is important that patients having this type of allergy test must not use anti-histamine medication for several days prior to the test. Blocking histamine reactions through medication may interfere with important readings. If a reaction happens (usually a red itchy wheal or bump) it is taken as a reliable ‘YES’ to the presence of IgE released histamine. It is not confirmation of an allergic disease. Many people can have positive skin prick test reactions without allergy symptoms. This is why it so important to have allergy testing carried out in a clinical setting with the background notes of the patient’s medical history available. In most cases, skin prick testing is available in an allergy specialist’s clinic or hospital setting.
Blood tests, often called RAST, CAP-RAST or specific-IgE, measure the exact amount of circulating levels of IgE antibody in the blood. In this test, a doctor or nurse can request either the total amount of IgE in the blood (adding all triggers together) or specify just those allergens they suspect may be triggering symptoms, such as house dust mites, cat, dog or from a wide-range of different allergens, including foods, tree pollen, grasses, moulds or fungi. With the test results, the doctor can confirm the relative levels of allergic sensitivity to various suspected triggers, and, in conjunction with a clinical history and examination, tailor treatments and advice on avoidance techniques to improve symptoms. If the results are negative and symptoms persist, further investigations may be required. This type of allergy testing can take a week or two to come back from the laboratory. Unlike skin prick testing, there is no need to stop taking anti-histamines. These tests are usually routinely available and can be requested by a family doctor or his nurse, just like any other blood test. The important thing is that whoever requests the test, takes a full allergy history to help interpret the results.
Allergy symptoms can threaten quality of life, yet allergy testing is often ignored in treating or diagnosing allergic disease. Here again, the Royal College of Physicians speaks out about the consequences.
‘Until blood tests became widely available, general practices and hospitals usually had little, if any, resources for establishing the presence (or absence) of sensitisation to specific allergens. In consequence, most allergic disease has been treated with drugs, with little attention being paid to establishing causative agents and allergen avoidance strategies’.
The time honoured first-step in treating allergy is avoidance of known triggers.
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 fewer allergic reactions or the reactions should be 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. Over-the-counter antihistamine tablets, such as fexofenadine (Allegra Allergy), loratadine (Alavert, Claritin), cetirizine (Zyrtec Allergy) and others, as well as antihistamine syrups for children, are available. Prescription antihistamines taken as a nasal spray include azelastine (Astelin, Astepro) and olopatadine (Patanase).
- Corticosteroids delivered as a nasal spray can reduce inflammation and control symptoms of hay fever. These drugs include fluticasone propionate (Flonase), mometasone furoate (Nasonex), triamcinolone (Nasacort AQ), ciclesonide (Omnaris) and others. 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, glaucoma 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 actually make nasal congestion worse.
- 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 of montelukast include upper respiratory infection, headache and fever. Less common side effects include behavior or mood changes, such as anxiousness or depression.
- Immunotherapy. You can “train” your immune system not to be sensitive to an allergen. This is done through a series of allergy shots called immunotherapy. One to two weekly shots expose you to very small doses of the allergen, in this case, the animal protein that causes an allergic reaction. The dose is gradually increased, usually during a three- to six-month period. Maintenance shots are needed every four weeks for three to five years. Immunotherapy is usually used when other simple treatments are not satisfactory.
- Nasal irrigation. You can use a neti pot or a specially designed squeeze bottle to flush thickened mucus and irritants from your sinuses with a prepared saltwater (saline) rinse. If you’re preparing the saline solution yourself, use water that’s contaminant-free — distilled, sterile, previously boiled and cooled, or filtered with a filter that has an absolute pore size of 1 micron or smaller. Be sure to rinse the irrigation device after each use with contaminant-free water, and leave open to air-dry.
Dust mites are tiny microscopic relatives of the spider and live on mattresses, bedding, upholstered furniture, carpets and curtains.
These tiny creatures feed on the flakes of skin that people and pets shed daily and they thrive in warm and humid environments.
No matter how clean a home is, dust mites cannot be totally eliminated. However, the number of mites can be reduced by following the suggestions below.
Preventive Strategies for Dust Mites
- Use a dehumidifier or air conditioner to maintain relative humidity at about 50% or below.
- Encase your mattress and pillows in dust-proof or allergen impermeable covers (available from specialty supply mail order companies, bedding and some department stores).
- Wash all bedding and blankets once a week in hot water (at least 130 – 140°F) to kill dust mites. Non-washable bedding can be frozen overnight to kill dust mites.
- Replace wool or feathered bedding with synthetic materials and traditional stuffed animals with washable ones.
- If possible, replace wall-to-wall carpets in bedrooms with bare floors (linoleum, tile or wood) and remove fabric curtains and upholstered furniture.
- Use a damp mop or rag to remove dust. Never use a dry cloth since this just stirs up mite allergens.
- Use a vacuum cleaner with either a double-layered microfilter bag or a HEPA filter to trap allergens that pass through a vacuum’s exhaust.
- Wear a mask while vacuuming to avoid inhaling allergens, and stay out of the vacuumed area for 20 minutes to allow any dust and allergens to settle after vacuuming.
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 dustproof 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 dryer for at least 15 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 below 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 work. Stay out of the vacuumed room for about two hours 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.
- Install a high efficiency media filter in your furnace and air conditioning unit. Look for a filter with a Minimum Efficiency Reporting Value (MERV) of 11 or 12 and leave the fan on to create a whole house air filter. Be sure to change the filter every three months.
In those in whom the cause is known and prompt treatment is available, the prognosis is good. Even if the cause is unknown, if appropriate preventative medication is available, the prognosis is generally good. If death occurs, it is usually due to either respiratory (typically asphyxia) or cardiovascular causes (shock), with 0.7–20% of cases causing death. There have been cases of death occurring within minutes. Outcomes in those with exercise-induced anaphylaxis are typically good, with fewer and less severe episodes as people get older.
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.