From 1974 to 1995, a retrospective evaluation was carried out by questionnaire of the systemic adverse reactions caused by pure Dermatophagoides farinae extract produced by Medical Acarology Laboratory, Shanghai Medical University (SMU-Df) during diagnosis and specific immunotherapy (SIT) with patients of asthma and rhinitis sensitive to mites. Of a total of 846,342 injections statistically analysed, 142 systemic adverse reactions were observed with an incidence 1.68/10,000 (CL=1.4-2.0/10,000), involving urticaria 0.82/10,000, severe attack of asthma 0.77/10,000, anaphylactic shock 0.07/10,000 (CL= 1.4-12.0/million), and angioedema 0.02/10,000. The time to onset of systemic reactions of the immediate type was <30 minutes in 32 cases (23%), and 1 and 2 hours in 6 cases each (8%); the time to onset of late response type was 3-48 hours in 23 case (59%) with highest incidence of severe asthmatic attacks; and there were 14 cases (10%) unknown. The systemic reactions occurred during skin tests in 18 subjects (13%), dose increasing phase in 96 cases (67%), dosage maintenance phase in 14 cases (10%), and unknown in 14 cases (10%). Among them, six cases were of anaphylactic shock and none of it causing death after emergency managements. The major cause of manifestation of systemic symptoms was coseasonal treatment when environmental exposure to allergens increased. The second cause was related to dosage errors, involving three subjects (3%) during the first injection overdose. The application of SMU-Df extract in skin tests and SIT of allergic disorders sensitive to mites during 22 years in this country indicated that the efficacy and safety of the extract are comparable to similar Df extract of foreign companies with very low risk of systemic adverse reactions. Selection of patient and medical professionals specially trained for SIT will be the key factors in making treatment successful and safe. SIT is an integral part in the mangement of asthma and rhinitis, and is more effective in children and young adults than later in life. A new phase of SIT—preventive allergy treatment (PAT)—for management of childhood asthma and other allergic disorders is a great challenge for allergologists.