Dust mites are perhaps the most common cause of perennial allergic rhinitis.
Dust mite allergy usually produces symptoms similar to pollen allergy and also can produce symptoms of asthma. Rather than a single substance, so-called house dust is a varied mixture of potentially allergenic materials. House dust also contains microscopic mites. These mites, which live in bedding, upholstered furniture, and carpets, thrive in summer and die in winter. In a warm, humid house, however, they continue to thrive even in the coldest months.