Objective To explore the possible influencing factors of clinical allergic reactions related to breviscapine injection in the real world. Methods A retrospective nested case-control study design and a symmetrical analysis method of prescription sequence were adopted. Based on the information management system of 37 tertiary first-class hospitals across the country

patients with suspected allergic reactions after using breviscapine injection were included

and data on admission

disease diagnosis

doctor′s orders

and treatment outcomes were collected to build a data warehouse. Cases whose outcome was suspected of allergy were the case group

and those whose outcome was non-allergic in the same cohort under certain conditions were the control group. The variables of suspected allergic reaction were combined disease（top 10 of frequency）

combined medication（top 10 of frequency）

length of hospital stay

duration of treatment

and dose of medication. Logistic regression method was used to explore the correlation among patients′ combined diseases

combined medications

single and daily doses of medications

duration of medication

length of stay in hospital

and suspected allergic reactions. Results The final case group included 270 cases

and the control group included 1350 cases. The regression coefficients of lumbar intervertebral disc herniation and lung infection in combined diseases were 0.29363912

0.14228938（P<0.05）

and the regression coefficients of potassium chloride and omeprazole in combined medication were 0.13004015 and 0.08152833（P<0.05）

respectively. The regression coefficient of single time overdose was 0.09793825（P<0.05）. A positive coefficient indicates that the variable was "yes"

or when this level was taken

the possibility of adverse reactions was high compared to the control group

which was the influencing factor of suspected allergic reactions. Conclusion Combined with prolapse of lumbar intervertebral disc

pulmonary infection

combined use of potassium chloride

omeprazole

single-time overdose are possible influencing factors for suspected allergic reactions when using breviscapine injection.