40 patients with bronchial asthma in Bach Mai hospital from 6/1998 to 5/1999 and 31 healthy people without allergy. Methods: finding the allergic history and skin test. The results: 52.5% of patients had his own allergic history; 42.5% of patients had a family history; 37.3% of patients had positive skin tests to foreign bodies of house dust mite; 32.5% of patients had allergic antibody against foreign bodies of house dust mite was more 30%. Among methods of specific diagnosis of allergy, there was a close relation between skin test and reaction of decomposition of mastocyte.