Dust mites require certain conditions beyond a food supply in order to thrive and reproduce. Temperature and humidity are the most critical factors, but dust-collecting floor-coverings and objects give them cozy refuges. That is why your bed can be such a good home and cause you to have allergies. Dust mite mattress covers protect you from dust mites in your bedding.
Temperature For Dust Mites
Studies have found that human beings generally prefer temperatures ranging between 18 and 20 degrees Celsius (64-72 Fahrenheit), and 30-70 percent relative humidity. What a coincidence then, that your comfort zone is nearly identical to that of dust mites! The North American house dust mite, Dermatophagoides farinae, enjoys life most at 19-30 C (65-76 F), and 70-80 % humidity. It’s European cousin, Dermatophagoides pteronissinus, likes things a little warmer, between 22 and 33 C (66-79 F). Those are not only optimal conditions for the mites, but also for xerophyllic fungi.
At one time it was thought that dust mites could not prosper without the help of certain xerophyllic (“dry-loving”) fungi, especially those in the genus Aspergillus. Seventy percent humidity may not seem “dry” to us, but the term “xerophyllic” means that no liquid water is necessary for the organism to live. The fungi supposedly break down the fat content of shed skin cells, making them more easily digestible for the house dust mites. This relationship between mites and fungi has largely been discredited, and in fact the fungi can actually inhibit the movement of mites by clogging the spaces between fibers of the mattresses and linens where the mites live. The reproductive potential of dust mites also decreases substantially with increased proliferation of fungi.
Relative humidity is the term for the level of moisture saturation in the air. The higher the humidity the more thick and “sticky” the air feels to human beings. Excessively low humidity causes our lips to chap and allows static electricity to build. House dust mites prefer humidity on the high side, but not so high that their fungal competitors overwhelm the skin flake food that both organisms eat. The mites can survive below 60 % humidity, but not very well.
Dust mites certainly find our beds to be a great place to live, surrounded by the flakes of skin we shed during sleep, and because the mattress, sheets, and blanket are often warmer and more moist than other places in the average household. Still, dust mites survive elsewhere. Carpeting and area rugs, especially deep pile (“shag”) types, can harbor large populations of dust mites. Plush toys (“stuffed animals”) can also accumulate dust and dust mites. Couches, sofas, and other upholstered furniture likewise trap dust, dust mites, and their excreted waste pellets. The place that your dog or cat habitually sleeps is likely to be another “dust mite central,” too.
Dust mites are in the family of mites collectively referred to as “feather mites,” and it comes as no surprise that they should be found in the homes of non-human animals, too. Indeed, house dust mites are often present in the nests of birds and wild mammals as well.