2. Relationship between dust mites and allergic asthma/allergic rhinitis
Dust mites are one of the most important common inhalant allergens. Allergic reactions to dust mites can occur at all ages, and the incidence of their allergic reactions is increasing, and dust mites are still the predominant allergen in allergic asthma in infants and children.
Dust mites are very closely related to allergic asthma/allergic rhinitis, as evidenced by.
(1) Prevalence of dust mites in the living room
The dust mites referred to in this review include the house dust mite and the dust mite, which are the two most important types of dust mites and belong to the genus Dust mite. It is internationally agreed that the distribution of the dominant mite species varies in different geographical locations and living environments, but worldwide, the most dominant mites in indoor areas are dust mites and house dust mites.
(2) The onset, development and persistence of symptoms of most allergic asthma are closely related to dust mite allergy
There are about 160 million bronchial asthma patients worldwide, and the prevalence varies from 1% to 13% in various countries, and the prevalence in China is 1% to 4%, and it is generally believed that the prevalence in children is higher than that in adults. Allergic asthma accounts for 80% of asthma in infants and children, and 40%-50% of allergic asthma in adults. Among allergic asthma, the most common allergens are dust mites, cat hair and dog hair. Dust mite prick test is positive in 85% of asthmatic patients, while the positive rate in normal population is 5-30%. Epidemiological surveys around the world have shown that dust mite is the most important allergen among the three common allergens mentioned above, and most of the occurrence, development, acute onset and persistence of symptoms of allergic asthma are closely related to dust mite allergy, and dust mite allergy is a risk factor for asthma.
(3) Dust mite is the most dominant allergen in allergic rhinitis
Allergic rhinitis is a global health problem that is common worldwide, with a global prevalence of 10%-25%, and the number of sufferers is increasing; it can affect patients’ daily life, study and work efficiency, and cause a serious economic burden.
Many studies have shown that dust mites are the most important allergen in allergic rhinitis. In addition, due to the long-term induction of inflammation of the nasal mucosa, it further plays a role in the development of nasal polyps.
3.Dust mite control methods
Dust mite intervention methods have 3 related objectives.
(1) To reduce the total amount of live mites.
(2) Reducing the level of mite allergens.
(3) Reducing human exposure to the first two.
The method of achieving these 3 goals in a given room is influenced by many factors: most importantly, price, ease of implementation, importance of the particular source of exposure, safety of the chemical used, and potential efficiency (benefit) of using the intervention method. The methods used vary depending on one or more of these factors. When the number of mites in the room is extremely high and the patient has severe symptoms of allergic reactions, multiple methods are used simultaneously. Specific control methods and bases are as follows.
(1) Reduce the relative humidity in the room
Controlling the relative humidity (RH) below 50% is the most common method to control the level of mites and their allergens, because the surrounding RH is the most critical factor affecting the prevalence of mites. Field studies have shown that mites and mite allergen levels are rarely present in these dry areas of mountainous countries or the northern Middle East. Many studies have reported that seasonal fluctuations in mite and mite allergen levels parallel seasonal fluctuations in indoor relative humidity. In dry areas, the use of evaporative coolers to increase relative humidity is sufficient to sustain mite survival.
Recent studies have shown that indoor use of high-performance moisture absorbers and air conditioners to reduce relative humidity and total mite levels is both practical and effective. It has been found that it is also possible to maintain RH below 50% in humid temperate zones to reduce mite and their allergen levels. In addition, maintaining RH below 50% during the day, even if RH is greater than 50% for 2-8 hours, is effective in limiting the total amount of dust mites and their allergens. To completely stop dust mite growth when RH is at 75%-85% for a day, RH should be below 35% for at least 22 hours a day.
The use of high performance moisture absorbers and air conditioning units in temperate zones can maintain RH below 50%. This may be the only approach needed within this environment. In this low humidity environment, new carpets, mattresses, pillows, and sofas do not help mites grow. In rooms where mites are already present, they will die in a dry environment, and over time, routine vacuuming and doing cleaning in the above mentioned areas will reduce allergen build-up. In some zones, there may be differences in dominant mite and dominant mite allergen levels between each home simply because of differences in humidity. In humid tropical areas, the practicality and effectiveness of vacuuming needs to be verified.
(2) Use of packing covers
Packing mattresses and pillows with special mite resistant materials is an effective way to reduce exposure to dust mites and their allergens. For allergy sufferers, this method is recommended, with packaging materials consisting of plastic, breathable materials, very fine fabric fibers or non-fabric synthetic materials. When purchasing pillow and mattress packing materials, the pore size of the fabric is very important. The ideal material should be a comfortable, breathable fabric that is permeable to steam and can stop mites and mite allergens from passing through. Tests have found that fabric pore sizes less than 10 microns can reduce the ability of Der f 1 and Der p 1 to pass through. The width of young mites is generally greater than 50 microns, so fabrics less than or equal to 20 microns can prevent the passage of all mites. vaughan et al. 16] confirmed the anti-mite properties of these commercially available special fabrics and synthetics by electron microscopy.
Rains et al. found that: new synthetic material pillows are more likely to accumulate Der p 1 than new feather pillows after 1 year of use. tests on dust mite allergens found that: non-feather pillows contain 5 times higher dust mite allergens than feather pillows, and their Der p 1 is 8 times higher. The reason for this may be that the fabric covering the surface of feather pillows is very tight, preventing dust mites from entering and reproducing inside. If this theory proves to be correct, then all pillows should have tight coats.
(3) Washing, drying and dry cleaning of bedding
Bed sheets, pillowcases, blankets, mattress covers washed once a week in hot water equal to or higher than 55°C can kill mites and remove most mite allergens. When washing things in hot water to prevent scalding. Washing with warm or cold water cannot kill most of the mites, however, it can remove most of the allergens because most of the allergens are water-soluble. The addition of 0.03% benzyl benzoate and 0.2% eucalyptus oil to the washing process can also kill mites, however, the odor of the laundry after washing with eucalyptus oil lasts for 2-3 days.
Recently, Tovey et al. reported that most mites and cat hair allergens could be removed with common laundry detergent at 25°C and for at least 5 minutes, however, the effectiveness of killing live mites is not known.
The key factor for killing mites in tumble dryers is to maintain the lethal temperature of mites for a long enough period of time. Rolling dryers can kill all mites if the temperature is greater than 55°C maintained for 10 minutes. The temperature and time lethal point of mites in air and water were found to be the same, and mites also died within 10 minutes at 60°C in air.
Dry cleaning is an effective way to kill mites, however, it does not remove all allergens.
In addition, Siebers et al. found that because Derp1 is soluble in water, the dust mite allergen Der p 1 was significantly reduced in hair after washing by conventional methods, so washing hair daily is also a good way to control dust mite allergens.
(4) Replacement of carpets, curtains and home decorations
Carpets, curtains and home décor fabrics accumulate debris debris and remain damp, providing an ideal habitat for mites to breed. In humid areas, carpets should be replaced with hard surfaces. Likewise, window (fabric) shades or blackout shades should be replaced with blinds, home décor fabrics should be replaced with vinyl or leather cushions, and furniture can be made of wood.
(5) Carpet vacuuming
If the family is not willing or financially not allowed to change the carpet, it should be vacuumed once a week and the vacuum cleaner bag should be replaced frequently. Vacuum cleaner bags should be double or high performance air filters or central vacuums with ends leading to the outdoors to avoid aerosol formation of allergens during vacuuming. Conventional vacuuming removes surface mites and allergens, but does not significantly reduce the number of live mites or remove deep-seated allergens. Conventional vacuuming is needed to remove dead mites and allergens after killing mites. Two studies have shown that mites and their allergens are easier to remove at low levels and densities and should therefore be vacuumed frequently.Vaughan et al. confirmed the mite protection performance of these high performance vacuums through tests.
Steam cleaning of carpets, if hot enough, can kill mites and remove surface allergens. However, steam cleaning often penetrates carpets to a limited depth and does not reach the fabric fibers of carpet pads or home furnishings, where large numbers of mites are present. In fact, steam cleaning may leave enough moisture in these areas to promote the growth of mites, which can have the opposite effect.
(6) Freezing soft toys and small items
Freezing soft toys and small items (such as pillows and special clothing) at -17°C to -20°C for at least 24 hours is an effective way to kill mites on these items. After freezing in the home refrigerator, these items can be washed to remove dead mites and allergens. Leaving mattresses and pillows outside for 24 hours in colder zones is also a recommended method of killing mites.
(7) Air cleaning/filtration
Mite allergens are mainly associated with dust particles larger than 20 microns in diameter. These particles become airborne when airflow appears disturbed, however, they quickly settle down again. Therefore, air cleaning or filtration in a room without air disturbance does little to capture mite allergens and should not be recommended.
(8) Duct cleaning
There are no reports or comments on whether duct cleaning is used as a method of mite and allergen removal. Because mites generally do not reside in HVAC systems, this operation may not be necessary for mite removal. There is a recent preliminary report indicating that for central air conditioning dust collected from vents little to no mite allergens were found. The idea that duct cleaning is beneficial to reduce mite allergens in the air coming from hot air vents needs to be thoroughly studied further. Duct cleaning may help to remove dust, debris, possible fungi and fungal allergens from the HVAC system.
(9) Ozone generator
Studies are also needed to determine the effectiveness and safety of ozone generators in killing mites or mite allergen denaturation. At this time, there are no reports of ozone affecting mite allergens.
(10) Chemical agents
The results in the use of chemical agents to remove mites and their allergens are inconsistent. Some studies have shown the ability to reduce allergen concentrations, others have shown poor results. The key issue in the use of chemical agents indoors is the safety of the agent, the form of the efficient product in the active ingredient in the agent. The product must be able to deliver its active ingredient directly to the place where the mites live. The use of acaricides such as: benzyl benzoate, disodium octaborate tetrahydrate, thorium reagent, Permethrin, denaturant, etc. It has been found that: there is no mutual symmetry between good active compounds and good mite and allergen control.
(11) Dust mite control as part of the overall treatment of allergic diseases
Mite allergen control should be recommended for patients with perennial allergic rhinitis, asthma or atopic dermatitis who are allergic to mites and whose disease cannot be controlled by simple general or inhalation therapy. The recommended approach should depend on the extent of the patient’s disease, the climatic conditions where the patient lives, and the individual’s living environment.
In the vast majority of cases, this includes distinguishing priorities of mite removal methods, education about them, and the purpose of treatment (see table below). Educate patients in all areas, and develop checklists if necessary. These forms may encourage patients to decide which approach they will use first or can afford, or to use both approaches first; they are also encouraged to document the progress made.
In general, all patients should be advised to use coats for mattresses and pillows and to change bedding that can be washed in hot water; bedrooms should be adjusted to reduce space for mite growth and allergen accumulation. Controlling humidity is not simple, but, as a medium to long-term goal, it needs to be discussed with the patient. In addition, if the patient is preparing to move, the patient should be advised on simple and effective controls for mites and other allergens in the new home.
In summary, dust mites are the single most important source of indoor allergens in dust in the vast majority of warm and humid parts of the world. Because dust mites are so closely associated with allergic asthma, allergic rhinitis and atopic dermatitis, de-miting and mite allergens is essential, especially when moderate to severe symptoms are present. Beds, carpets and home furnishings are the 3 most important areas when it comes to mite removal.