How to Adapt the Home Environment for People Sensitized to House Dust Mites
Introduction
In the 1920s, house dust was identified as a source of allergens. However, it was not until 1967 that mites were discovered in household dust [1]. Since then, numerous protein allergens originating from house dust mites (HDMs), primarily from their feces, have been identified and isolated. Patients sensitized to HDM allergens usually experience symptoms throughout the year, and pharmacological treatment alone may be insufficient. This article reviews methods for reducing exposure to HDM allergens in the immediate living environment—the home.Prevalence of House Dust Mite Sensitization
In Pakistan, skin prick testing (SPT) has identified HDM sensitization in as many as 81% of individuals with symptoms suspected to be allergic in origin [2]. It is estimated that approximately 1–2% of the global population (65–130 million people) has hypersensitivity to HDMs [3, 4]. As many as 50% of patients with asthma are also sensitized to HDMs [4]. In a publication by Bousquet and colleagues, HDM sensitization was investigated across 35 centers. The prevalence of sensitization varied from 4.8% to 36.8% among centers located in different regions of Europe, the United States, and New Zealand [5].Types of House Dust Mite Avoidance
The first type of HDM avoidance includes all methods aimed at reducing an allergic individual's exposure to allergens, specifically HDM allergens. The main methods for reducing allergen exposure include:-
Using special protective covers for pillows and mattresses;
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Controlling indoor humidity;
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Using air purification devices;
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Removing carpets;
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Regularly vacuuming living areas [1, 6].
Primary Prevention
Primary prevention aims to minimize exposure to HDM allergens from early childhood. It has been observed that in countries where environmental conditions are unfavorable for HDMs, mite allergens do not contribute to the development of bronchial asthma symptoms [9]. This suggests that children raised in areas with insufficient HDM populations may not develop sensitization to these allergens. However, primary allergen avoidance is often impossible, particularly when living in an older apartment building. The 2018 international consensus on allergic rhinitis (AR), developed by allergists and otorhinolaryngologists, reviewed six studies investigating the relationship between exposure to HDM allergens during pregnancy and early childhood and the development of AR [10]. Four of the six studies found no association between the development of AR and early exposure to HDM allergens [11–14]. Consequently, the authors concluded that further studies are needed to establish the precise relationship between early HDM exposure and AR [10]. There is currently insufficient clear evidence supporting the effectiveness of this method, and its implementation can be particularly challenging. Therefore, greater emphasis should be placed on methods that help control symptoms of an existing allergic disease rather than those intended to prevent sensitization [1].Use and Washing of Special Mattress and Pillow Covers
People spend approximately one-third of their lives sleeping, making it particularly important to reduce allergen exposure during sleep. Around 2000, specialized technologies were developed that made it possible to manufacture extremely tightly woven fabrics through which HDMs cannot penetrate [12]. Mattress and pillow covers made from these materials remain breathable and do not impair sleep quality. Several studies have investigated the effectiveness of these protective covers. Ghazala and colleagues reported that the covers significantly reduced HDM allergen levels [15]. Similar conclusions were reached by Gøtzsche [16] and Terreehorst and colleagues [17]. Nevertheless, this method alone is insufficient to improve allergic symptoms [15–18]. To further reduce HDM exposure, it is recommended that covers be washed at least every two weeks at a temperature of no less than 55°C [19, 20]. Ideally, the covers should be dried in an electric tumble dryer, which theoretically should kill all living mites [20, 21].Indoor Humidity Control
It has long been observed that people living in mountainous regions or deep inland are less frequently sensitized to HDMs than those living along ocean or sea coasts [22]. Studies have shown that HDM allergen concentrations are lower at an average relative humidity of 44% than at 76% [23]. Maintaining an average indoor relative humidity below 50% is considered sufficient to control HDM populations [1, 24–26]. It is important to recognize that even in geographical regions where HDMs are relatively uncommon, cooling homes with evaporative coolers may create favorable conditions for HDM reproduction [27].Air Purification
Because HDM allergens are classified as inhalant allergens, it is reasonable to expect that purifying indoor air may provide benefits. There are several main approaches to air purification: electrostatic filtration and mechanical filtration using high-efficiency particulate air (HEPA) filters. In many cases, electrostatic air purifiers generate ozone. In addition, electrically charged particles, including allergens, may settle on walls. Charged HDM allergens and other particles accumulate on electrostatic filters, causing them to become contaminated and requiring regular washing or replacement [1]. These filters can also be used to measure HDM allergen levels [28]. In practice, HEPA filters are used much more frequently. These filters mechanically remove particles as small as 0.1 µm. It is important to note that air discharged from the filter may disturb dust deposited on the floor. Therefore, HEPA filters should be placed in clean areas without carpeting. When used properly, HEPA filters can improve symptoms of allergic diseases in individuals sensitized to household allergens. However, this method is most effective when combined with other HDM avoidance measures [6, 29–31].Vacuum Cleaning
When vacuum cleaners were first introduced into households, it was expected that they would thoroughly clean carpets without the need to lift or remove them. However, it was later discovered that vacuum cleaners cannot remove living house dust mites (HDMs) from carpets because of the unique structure of their legs [32]. Vacuum cleaners equipped with steam-cleaning functions should theoretically remove living HDMs. However, accumulated debris prevents steam from penetrating the deeper layers of carpets. Furthermore, steam cleaners are designed to limit deep steam penetration to preserve carpet colors [1]. Studies have shown that vacuum cleaners equipped with HEPA filters significantly reduce HDM allergen levels [33, 34].Removal of Carpets, Curtains, and Upholstered Furniture
Numerous studies have confirmed that mattresses and carpets are important sources of HDM allergens [18, 19, 34, 35]. Therefore, carpets and upholstered furniture should be removed from the home, or at least from the bedroom. Alternatively, furniture should be covered with HDM-resistant fabrics that are washed weekly. When selecting upholstered furniture, preference should be given to materials that are easy to clean, such as leather or synthetic upholstery [36, 37].Temperature-Controlled Laminar Airflow During Sleep
During sleep, the human head acts as a heat source, creating a temperature gradient that is highest around the face. As a result, warm air rises from the head, carrying allergens from pillows and bedding into the breathing zone, where they may be inhaled. A temperature-controlled laminar airflow system delivers filtered, cooler air above the head, altering the temperature gradient and redirecting allergens away from the breathing zone (Figure 1). Clinical studies have reported benefits of this method in patients with allergic bronchial asthma and allergic rhinitis [8, 38, 39].Use of Acaricides
Acaricides are pesticides used to kill mites. Several types are used in household environments, including macrocyclic lactones, synthetic pyrethroids, carbamates, organophosphates, and benzene hexachloride [40]. To maintain their effectiveness, these pesticides would need to be sprayed on mattresses, carpets, and upholstered furniture every 1–3 months [41]. In a systematic review by Nurmatov and colleagues, acaricides were identified as the most effective individual method of HDM avoidance [18]. However, because people frequently come into close contact with surfaces treated with acaricides and their effects are relatively short-lived (1–3 months), acaricides are not recommended for eliminating HDMs in the home [41].Pheromone-Based Dust Mite Traps
Pheromones influence various animal behaviors, including aggression, escape from danger, mate seeking, and mating [42]. Based on these properties, researchers have proposed using pheromones to develop traps for HDMs [43]. Research on HDMs has identified neryl formate as an attractant for two major HDM species, D. farinae and D. pteronyssinus [44]. This substance should be sprayed onto a specially designed trapping fabric, which is then placed on the bed. After a specified period, the fabric should be removed and washed at a temperature of at least 60°C. During the first month, this procedure should be repeated once weekly for the first three weeks and subsequently once a month [45].Clinical Effectiveness
Several challenges arise when evaluating the effectiveness of HDM avoidance methods:-
Some study participants were sensitized not only to HDMs but also to other inhalant allergens present in their homes.
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The interventions used in both control and treatment groups were sometimes so intensive that differences between the groups were practically impossible to detect.
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The interventions did not significantly reduce HDM allergen levels, making assessments of clinical effectiveness questionable.
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Some participants had only minimal clinical manifestations of allergic disease before entering the studies, making subsequent changes difficult to evaluate [17].
Conclusion
House dust mites are present in virtually every home, although they thrive particularly well in warm and humid environments. Numerous HDM avoidance methods have been described, but the best results are achieved by combining several approaches, such as using special mattress and pillow covers and controlling indoor humidity. The greatest challenge in household environments is achieving a clinically meaningful reduction in HDM allergen levels. Without such a reduction, the clinical benefits of avoidance measures remain uncertain. It is important to emphasize that HDM allergen avoidance strategies do not replace conventional pharmacological treatment, although they may help improve symptom control. Patient education is particularly important. Patients should understand which environmental conditions favor HDM reproduction and how simple measures can reduce exposure to HDM allergens. Linas Griguola, MD, and Laura Malinauskienė, Associate Professor Clinic of Chest Diseases, Immunology and Allergology Institute of Clinical Medicine, Faculty of Medicine, Vilnius University Read more in Internistas, supplement Allergy. Asthma. Immunology, 2018.
References:
1. Wilson JM, Platts-Mills TAE. Home Environmental Interventions for House Dust Mite. J Allergy Clin Immunol Pract. 2018 Feb;6(1):1–7.
2. Shafique RH, Akhter S, Abbas S, Ismail M. Sensitivity to house dust mite allergens and prevalence of allergy-causing house dust mite species in Pothwar, Pakistan. Exp Appl Acarol. 2018 Mar 10;
3. Colloff MJ. Dust Mites. Springer Science & Business Media; 2010. 592 p.
4. Calderón MA, Linneberg A, Kleine-Tebbe J, De Blay F, Hernandez Fernandez de Rojas D, Virchow JC, et al. Respiratory allergy caused by house dust mites: What do we really know? J Allergy Clin Immunol. 2015 Jul 1;136(1):38–48.
5. Bousquet P-J, Chinn S, Janson C, Kogevinas M, Burney P, Jarvis D, et al. Geographical variation in the prevalence of positive skin tests to environmental aeroallergens in the European Community Respiratory Health Survey I. Allergy. 2007 Mar;62(3):301–9.
6. Wright LS, Phipatanakul W. Environmental remediation in the treatment of allergy and asthma: latest updates. Curr Allergy Asthma Rep. 2014 Mar;14(3):419.
7. Garritsen FM, ter Haar NM, Spuls PI. House dust mite reduction in the management of atopic dermatitis. A critically appraised topic. Br J Dermatol. 2013 Apr;168(4):688–91.
8. Warner JO. Use of temperature-controlled laminar airflow in the management of atopic asthma: clinical evidence and experience. Ther Adv Respir Dis. 2017;11(4):181–8.
9. Sporik R, Ingram JM, Price W, Sussman JH, Honsinger RW, Platts-Mills TA. Association of asthma with serum IgE and skin test reactivity to allergens among children living at high altitude. Tickling the dragon’s breath. Am J Respir Crit Care Med. 1995 May;151(5):1388–92.
10. Wise SK, Lin SY, Toskala E, Orlandi RR, Akdis CA, Alt JA, et al. International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis. Int Forum Allergy Rhinol. 2018 Feb;8(2):108–352.
11. Kulig M, Klettke U, Wahn V, Forster J, Bauer CP, Wahn U. Development of seasonal allergic rhinitis during the first 7 years of life. J Allergy Clin Immunol. 2000 Nov;106(5):832–9.
12. Corver K, Kerkhof M, Brussee JE, Brunekreef B, van Strien RT, Vos AP, et al. House dust mite allergen reduction and allergy at 4 yr: follow up of the PIAMA-study. Pediatr Allergy Immunol Off Publ Eur Soc Pediatr Allergy Immunol. 2006 Aug;17(5):329–36.
13. Illi S, Weber J, Zutavern A, Genuneit J, Schierl R, Strunz-Lehner C, et al. Perinatal influences on the development of asthma and atopy in childhood. Ann Allergy Asthma Immunol. 2014 Feb 1;112(2):132-139.e1.
14. Schoos A-MM, Chawes BL, Jelding-Dannemand E, Elfman LB, Bisgaard H. Early indoor aeroallergen exposure is not associated with development of sensitization or allergic rhinitis in high-risk children. Allergy. 2016 May;71(5):684–91.
15. Ghazala L, Schmid F, Helbling A, Pichler W, Pichler C. Efficacy of house dust mite- and allergen-impermeable encasings in patients with house dust mite allergy. Allergologie. 2004 Jan 1;27:26–34.
