Patients with asthma and allergic rhinitis have long been known to have positive skin test responses to house dust. In the 1960's it was shown that the dust mite was the most important source of allergen in house dust. Techniques for growing dust mites in the laboratory enabled the preparation of dust mite allergen extracts. Identification of the major allergens of dust mite along with specific skin test methodology has resulted in standardized dust mite allergen extracts for diagnostic and therapeutic use. Numerous epidemiologic studies have demonstrated the importance of sensitization to dust mite as risk factors for asthma and allergic rhinitis symptoms.