BACKGROUND: Skin prick test has been the primary diagnostic tool used to recognize causative allergens, and there is some evidence that skin reactivity to allergens can be altered by changes in the environment. OBJECTIVE: We performed this study to evaluate whether there are changes in skin reactivity to inhalant allergens among patients with bronchial asthma. MATERIALS AND METHOD: We reviewed the skin prick test results of 384 bronchial asthmatics tested in the early 1990s (June 1992-May 1994) with 52 common inhalant allergens and compared the results of 500 asthmatics tested in the mid 1980s (Jan 1984 - May 1987) with the same kinds of allergens provided by the same manufacturer. RESULTS: Of the 384 subjects tested in the early 1990s, 276 subjects(71.9%) had positive reaction to one or more inhalant allergens and the positive rate was not different from that of the mid 1980s(74%). But, skin reactivity to pollens was significantly increased. In individual allergens, house dust mite(D. farinae and D. pteronyssinus) was the most reactive allergen (52.3%, 43.2% respectively) in the early 1990s. Significant differences in skin reactivity to ragweed (10.0% vs 22.1%, p<0.05) and cockroach (12.7% vs 25.0%, p<0.05) were found when the results of the 1980s and the 1990s were compared. CONCLUSION: House dust mite was the most important allergen in asthmatics from the mid 1980s to the early 1990s. There was increased sensitization to cockroach and ragweed allergen in the early 1990s. Further prospective immunologic and environmental studies are recommended for proper interpretation of the changes in skin reactivity.