Substance P (SP) is a multipotent neuropeptide that affects the proliferation, activation and motility of keratinocytes and fibroblasts (Fbs). SP in pulmonary and synovial cells is degraded by CD10, a 90- to 110-kDa cell surface zinc-dependent metalloprotease. However, the expression and function of CD10 in human dermal Fbs have not yet been investigated in vivo and in vitro specifically with reference to SP. Our immunohistologic study revealed moderate to strong fibroblastic CD10 expression in the majority of psoriasis vulgaris (16/16), chronic eczema (15/16), lichen planus (18/20) and atopic dermatitis (4/5). Keratinocytes showed no CD10 expression in vivo and in vitro. Cultured Fbs constitutively expressed CD10 and SP. CD10 expression was augmented by external interleukin (IL)-1β and IL-22, but not by IL-8 and IL-17A in Fbs. SP production was enhanced in CD10 knockdown-Fbs (CD10ND-Fbs) compared with control-Fbs. In the presence of IL-1β or IL-22, the enhancement of SP production was more prominent in CD10ND-Fbs than in control-Fbs, suggesting the down-modulating activity of CD10 on SP in cytokine-mediated inflammation. In conclusion, fibroblastic CD10 expression may down-regulate skin inflammation by degrading SP or reducing its level in the dermal microenvironment.