For effective management of atopic dermatitis (AD), it is important to introduce a therapeutic agent, which although having the fewest side effects, has the greatest anti-inflammatory effect. In the course of screening anti-inflammatory agents, we obtained BSASM, a mixture of several plant extracts. This study was designed to investigate the AD-mitigating effect of BSASM in patients, as well as its anti-inflammatory and immunomodulatory effects in an in vitro experiment. The anti-inflammatory effects of BSASM were evaluated by the level of production of proinflammatory cytokines. Clinical evaluation was also done using eczema area severity index (EASI) score in AD patients. BSASM inhibited LPS-induced activation of NF-kappaB promoter. In addition, LPS-induced an increase of IL-8, and the TNF-alpha production in THP-1 cells was also inhibited. These results suggest that BSASM has an anti-inflammatory activity. A clinical study in patients with AD showed that BSASM induced a reduction of EASI score, degree of pruritus, and TEWL on both the antecubital fossa and abdomen. Besides, BSASM had no irritative or allergic effects. Based on these results, we conclude that BSASM has anti-inflammatory and AD-mitigating effects.