Dust mites are teeny, tiny bugs that live in household dust. You have to be pretty small to live in dust — and they are. You actually need a microscope to see them! So if you can't even see them, what's the problem? Well, people can be allergic to dust mites and their droppings. This stuff gets into the air and then can get into someone's lungs. Dust mites don't bother most people, but they can make breathing problems worse for someone with asthma. It can be tough to get rid of dust mites because they get into soft places like pillows, blankets, mattresses, and stuffed animals.