Objective: To analyze the composition principles of the external use prescriptions for urticaria collected in 〈The Prescription Dictionary of Traditional Chinese Medicine〉. Method: The external use formulas used for urticaria in 〈The Prescription Dictionary of Traditional Chinese Medicine〉 were collected

then entered the Traditional Chinese Medicine Inheritance Support System (TCMISS;V1.1). By using data mining methods

composition principles of the prescriptions were analyzed. Result: Based on the analysis of 134 cases of external use formulas

the frequency of each herb included in the database was computed

twenty-seven core combinations and 5 new prescriptions were mined from the database. Conclusion: The composition principles of the formulas for urticaria collected in 〈The Prescription Dictionary of Traditional Chinese Medicine〉 were summarized. This would be the foundation for further research and development of new drugs for treating urticaria.