What is a dust mite allergy?

A house dust mite allergy is triggered by house dust mites and their excrement. House dust mites are one of the most significant allergy triggers (1). One characteristic of a dust mite allergy is that it causes allergic symptoms throughout the entire year.

House dust mites occur nearly everywhere where people live. They are invisible to the naked eye. They are tiny, eight-legged spider-like creatures measuring 0.2-0.4 mm in size. They live in temperatures of 15 to 32° Celsius and require a high humidity of 70-80 %.

House dust mites are a natural part of the ecosystem of the "living environment". They are not present because of a lack of hygiene and they do not transmit any diseases. The life expectancy of these tiny creatures is two to four months. During this time, they produce 200 times their own weight in allergen-containing mite excrement.

In living environments, mites can be found everywhere where they find the necessary humidity, warmth, darkness and food. Dust mites feed on dead skin particles. One adult human produces approximately 1.5 grams per day, which can feed approximately 100,000 dust mites. Mites find ideal living conditions in the bed. Mites and excrement accumulate mainly in pillows, in the comforter and in the mattress. However, they also get into the dust and are therefore distributed on carpets, floors, curtains and sofas. The dust is whirled around each time we move. Vacuuming, in particular, increases the allergy load in the room air, because the particles of the excrement are so tiny that they are blown back into the environment through the exhaust air filter. Mites can hide particularly well in deep-pile carpets. These offer mites excellent protection and good chances for survival, because they can grip onto the fibers, meaning the vacuum cleaner has almost no chance to get them. (1).

With the start of warmer and humid weather in early summer, mites start to reproduce. Their population numbers peak by midsummer and the early months of fall. With the beginning of the heating period in fall, most house dust mites die because of the decreasing humidity. Despite this fact, the discomfort for people who are allergic to mites reaches a peak specifically during this time. Now, the maximum quantity of mite excrement has accumulated; this disintegrates and is distributed by the heated air throughout the living environment, together with dried mite particles. If someone with a mite allergy breathes these harmless substances, or if these substances enter this person's mucous membranes, they can trigger allergic symptoms.

The immune system of someone allergic to house dust mites reacts excessively to the various protein particles from the mites themselves and in the mite excrement. Their immune system falsely classifies these allergens as dangerous and forms antibodies of immunoglobulin E type, called IgE for short. During the course of the allergic reaction, various messenger substances such as histamine are released, which trigger allergic symptoms in various organs (nose, eyes, and lungs). With allergic rhinitis or hay fever, you suffer from nasal congestion, a runny or itchy nose, or the urge to sneeze frequently. If your eyes are reddened and watery, then this is caused by an allergic rhino-conjunctivitis. If the lower respiratory tract is affected and respiration is impaired through sudden difficulty breathing and coughing, it may be caused by allergic asthma.

The causes of house dust mite allergies are still unclear. Environmental factors, smoking, changed eating habits and excessive hygiene seem to promote the development of allergies. In addition, genetic predisposition plays a role. Children whose parents or grandparents already suffer from allergies are at an increased risk of developing an allergy (2). If you suffer throughout the year from allergic symptoms inside your home and you have a pronounced reaction to dust in your home, then a house dust mite allergy can be suspected.

Only an allergist can firmly clarify whether you are allergic to house dust mites.

He or she will first discuss your medical history with you. This means, the physician will discuss your ailments, how severe they are, when symptoms occurred for the first time, whether you only suffer from them during specific seasons of the year or all year round, the situations that increase or decrease your symptoms, and finally, whether and when you are completely free of symptoms. This information will give him or her important indications for the type of allergy and any possible trigger(s). In addition, he or she may want to know whether there are allergies in your family and the result of any previously attempted treatments.

The medical history gives the physician important information as to whether your symptoms are actually caused by an allergy and which allergens may be responsible for your symptoms. He or she will then try to discover the allergy triggers through a skin test. The most commonly used method is the so-called skin prick test. An intracutaneous test is used less frequently. In addition, the allergen-specific immunoglobulin E can be revealed in the blood by means of a lab test. Both the skin test and the blood test show only sensitivity to the respective allergen; a so-called sensitization. This is not the same as a dust mite allergy. Only if symptoms are present throughout the year, i.e., if the medical history corresponds to the diagnostics may it actually be a dust mite allergy.

A provocation test can also be conducted to confirm the skin test results or in the event that there is some doubt over the diagnosis. In this case, the respective allergen is applied in a highly diluted form directly to the effector organ (nose, lungs or eye) where the symptoms are evident. If the patient reacts to the allergen with typical allergic symptoms such as a runny nose, the urge to sneeze, watery eyes, then the diagnosis is certain and the allergen causing these symptoms is identified without doubt.

Your allergist will offer you three options to treat the allergy: avoidance of the allergen, antihistamines and a specific immune therapy. Ideally, the physician would combine these measures to contain your symptoms as swiftly and effectively as possible.

According to Deutsche Atemwegsliga [German Respiratory Society], the avoidance of allergens offers the best protection from allergies (2). The most important source for house dust mites and their allergens is the bed (3). Therefore, particular priority should be given to cleaning up the bed. By covering the mattress, the bed cover and pillows with special mite-impermeable covers (so-called encasing), the contact with allergy triggers, the mites and their excrement, is immediately and effectively stopped. This leads to a significant decrease in symptoms for people with house dust mite allergies, as scientifically proven for the intermediary encasing, ALLERGOCOVER®, in a double-blind, placebo-controlled study (3). Another study (4) points to the same outcome. The majority (more than 93 % of users) do not feel disturbed while sleeping or are only a little disturbed, and they evaluated the sleeping comfort of ALLERGOCOVER ® as good (4).

For some people with a dust mite allergy, symptoms may be sufficiently alleviated by using the encasing, making any additional therapy superfluous (3). In any case, they are a meaningful component in the treatment of any house dust mite allergy (2; 3).

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(2)  Allergische Erkrankung der Atemwege.pdf
(3)  Brehler R, Kniest F. Allergy Clin Immunol – J World Allergy Org 2006;18:15-19.
(4)  Müller-Scheven D, et al. Allergologie 1998;11:534-540.
(5)  Nielsen: Marktanteile Encasings Apotheken und Apothekenversand MAT 09/2013.