You can't see house dust mites, but you can feel their presence, mainly in the form of allergies such as eczema, coughs, blocked noses and asthma. These symptoms are frequently caused by these microscopically small creatures. House dust mites prefer to live in your mattress. So, when you settle down in bed for the night, spare a thought for the two million or so house dust mites under you. Whether you like it or not, you’re going on a date tonight with a dust mite.