A single gram of house dust (approximately half of a teaspoon) contains as many as 1,000 microscopic dust mites. The bed on which you sleep every night can contain millions of dust mites, and as a result there are vast amounts of dust mite droppings right where you sleep. Dust mites are the most common allergen-producing organisms found in homes. They live in your pillows, mattress, box spring, carpet, and upholstered furniture, and thrive in warm environments such as your bedroom. Dust-mite proof pillow, mattress, and box spring covers help prevent exposure to allergens and reduce the number of dust mites living inside the bedding.