Atopic dermatitis (AD) is a common inflammatory skin disease characterized by xerosis, pruritus and eczema. The role of probiotics in the prevention and the treatment of AD have been extensively studied in children with controversial results while there are few studies on an adult population. The aim of this randomized, double-blind, placebo-controlled study is to evaluate the clinical efficacy of the intake of a probiotic strain (Lactobacillus salivarius LS01) in the treatment of adult patients with AD. A group of 38 patients was treated with probiotics or placebo (maltodextrin) for 16 weeks. The study was performed from January (T0) to May, 2009 (T16). The assessment of efficacy was based on change in SCORAD (SCORing Atopic Dermatitis) index, dermatology life quality index (DLQI) improvement, cytokine production by PBMCs and ability to modify faecal microbial flora. No significant adverse events were recorded during the study. Patients treated with probiotics showed a statistically improvement of both clinical parameters (SCORAD p<0.0001 and DLQI p= 0.021) at the end of treatment (T16) compared with the placebo group. Furthermore, after four months of treatment there was a significant reduction of Th1 cytokines (IL-12+IFNgamma) (p= 0.03) and Th1/Th2 ratio (IL-12+IFNgamma/IL-4+IL-5) (p= 0.019) only in placebo-treated patients. A statistically relevant decrease of staphylococci in faeces of the probiotictreated group was also observed at the end of treatment. In our study, the administration of L. salivarius LS01 was well tolerated and was associated with a significant improvement of clinical manifestation and QoL. This probiotic strain could have an important role in modulating Th1/Th2 cytokine profiles and could be considered as an important adjunctive therapy in the treatment of adult AD.