Dust Mite has 8 legs and is at the same order “Araneae” as spider in classification. The body of a dust mite is invisible to the naked eye and can only be viewed under microscope. A typical dust mite measures about 100- 400 µm in length (almost 0.5 mm) and 300 µm in width. From recent research, three main kinds of house dust mites (Dermatophagoides pteronyssinus, Dermatophagoides farinae and Blomia tropicalis) are being one of the single greatest sources of allergies and are significant triggers of asthma attacks. The fecal matter, egg and the remains of dust mite can cause allergies too. Even worse, their tiny size enables them to spread fast and easily in air.
Ideal environment to dust mite growth – Our home
The warm and humid condition of Sub-tropical climate offers an ideal environment to dust mite growth at human home, especially when the temperature is between 20°C and 30°C; relative humidity between 60~80%.
(In general, the house dust mite cannot survive when the relative humidity is lower than 55% and the room temperature higher than about 50°C.)
In nowadays home environment, the centralized heating and the condensed moisture within a constrained house are enhancing the good condition to dust mite growth.
The box spring of a double bed can accommodate up to 2 million no. of mites and several pounds of fecal matter produced by mites. In other words, people are spending 1/3 of their lifetime, which is approximately the sleep time of people, being exposed and direct contact to dust mite and its allergens.
On the other hand, dust mites survive and reproduce easily in bedding (pillows, mattresses, box springs and comforters) where the essence of mite growth is provided:
（１）Adequent food - Dust mites feed on organic detritus such as flakes of shed human skin
（２）Optimal humidity - humidity generated by the human body during several hours of breathing and perspiring
（３）Optimal temperature – heat from human body
It is estimated that the weight of dust mites and their fecal matter in a pillow which has already been used for 2 years is about 10% of the weight of the pillow.
And one gram of dust may contain up to 1000 no. of dust mites and 200,000 fecal particles which are smaller and lighter than dust mite and can be inhaled more easily. When people are carry daily housing keeping and moving the bedding, these tiny particles may easily go into the respiratory system of human, even enter the primary bronchioles in lungs. As a result, human allergy symptoms like asthma attacks will be observed.
As we can see, dust mites survive and reproduce easily in bedding where optimal growth condition and food is present – sweating of human during sleeping and skin cells and flakes shed from man. The number of dust mite will increase with the service time of bedding. Therefore encasing the pillows, mattresses, box springs and comforters by allergen barrier will be the best way to control our exposure to dust mites and allergens
Info provided by allergy and asthma expert forum