The purpose of this study was to investigate the significance of contact allergen and aeroallergen sensitization in suspected allergic contact dermatitis (ACD), unclassified endogenous eczema (UEE) and non-atopic chronic urticaria (NACU). 63 cases of suspected ACD, 140 cases of suspected UEE and 21 cases of suspected NACU were patch tested with the standard series of Beijing Medical University and, if available, suspected materials as is. 22 such cases of ACD, 104 such cases of UEE and 42 such cases of NACU were intradermally tested with common aeroallergens. Patients with non-allergic skin disease served as controls. 85.7% of the suspected ACD patients, 57.9% of the suspected UEE patients and 52.4% of the suspected NACU patients were positive on patch testing, and the results in 81.0% of the suspected ACD patients and 23.6% of the suspected UEE patients were considered relevant. No patch test reactions in the NACU patients were considered relevant. 27.1% of the suspected UEE patients, 41.3% of the suspected ACD patients and 14.3% of the suspected NACU patients reacted to 2 or more contact allergens. High positive rates on aeroallergen intradermal testing were also found in suspected NACU (69.0%), UEE (49.0%) and ACD (59.1%) patients. These results support the conclusions that patients with allergic skin diseases will develop multiple sensitization, and that early detection and avoidance of sensitizing allergens is necessary. The exact rôle of aeroallergen sensitization in these diseases needs further study.