Dust mites, typically, don't induce the itch of bed bugs or spread diseases, but like their more annoying and dangerous breathren, they love the world we humans have created for them. They’re not parasites—they don’t suck our blood or burrow into our skin. They just munch on our dead skin and hair.
In the process, though, they shed and poop. And that’s the problem. Many humans are allergic to dust mite waste.
Dust mites love humans so much that they can reliably be expected to live wherever we live, including in our cars. As we jet around the world, so do the mites. A new genetic analysis of dust mites, published in PLoS ONE, reveals exactly why we are so allergic to their poop. The mites have developed a strong digestive enzyme to break down the dead cells they eat, writes Lina Zeldovitch for Nautilus. That enzyme ends up in the poop, which young mites eat for nourishment. But it also causes problems for us. Zeldovitch explains:
But for humans that poop is harmful. When it comes in contact with our skin or lands in our lungs, the enzyme erodes our cells as if they are food. “Those [fecal] particles are very small and they can be easily get airborne,” says [study author Pavel Klimov of Michigan University]. “They break up our delicate cell membranes and that causes allergies.” The reactions range from rhinitis (drippy nose), to atopic dermatitis (a form of eczema), to asthma.
The enzyme isn’t the only allergen in mite poo. There are probably 20 in total.
Perhaps more alarming, the study was conducted because people in Pakistan were being diagnosed with dust mite allergy. However, mites had never been recorded there. Turns out that was just an oversight—but a recent one. There are mites and they are closely related to those in the U.S. People are probably spreading mites from place to place as they jet around. You may have transported some hitchhikers yourself during holiday travel, for instance.
But look on the bright side: At least dust mites don’t set up colonies in human ears—most of the time.