Atopic dermatitis (AD) is a common inflammatory skin disease with recurring episodes of itching and a chronic relapsing course. Keishibukuryogan (KBG) is a traditional herbal medicine, composed of five kinds of medical plants and has been administered to patients with blood stagnation in Japan. This study investigated the effect of KBG on the disease activity in AD (n = 45) patients. AD patients were administered KBG for 4 to 6 weeks in addition to their prescribed medications. The results showed that the SCORAD index and VAS score were significantly decreased after the administration of KBG (P < 0.01). KBG also decreased the serum LDH level significantly (P < 0.01). The global assessment of the clinical response in SCORAD index showed that 88.5% of the patients with moderate improvement to excellent response (n = 26) had a high lichenification score (lichenification score ≥2 in SCORAD). On the other hand, only 42.1% of the patients with no improvement to mild improvement (n = 19) had a high lichenification score. Furthermore, long-term administration of KBG for 9-67 weeks showed a marked improvement in patients with a high lichenification score. Therefore, KBG was found to be effective against AD, particularly in cases presenting with lichenified lesions.