The fecal matter is very light and can stay air born for hours. The dust mites have sticky feet that cling to surfaces making it impossible to remove them by vacuuming the carpets or mattress. Vacuuming will remove dead mites and fecal matter but that matter is so microscopic that unless the vacuum has a HEPA filter that matter will escape through the paper bag and enter the air space adding to the allergic reaction. Controlling humidity is the single most important factor in maintaining the reproduction of dust mites. Purchase a hygrometer and check the relativity humidity in your home often.
Dust mites colonize in mattresses, carpets, and upholstered furniture.
They also are very fond of stuffed animals. Change the bedding often, removing the sheets like picking up a picnic blanket full of crumbs. Remove the sheets at the corners and roll carefully toward the center. Pick up the bundle and remove to the laundry. Handle carefully not to disturb the matter because when it becomes airborne it will contaminate the air space for up to eight hours.