Psoriasis is a chronic inflammatory skin disease affecting approximately 2-3 percent of the world population; it is characterised by hyperproliferation and hyperplasia of the superficial layers of the epidermis. Inappropriate signals released by the immune system determine an altered keratinocyte differentiation, resulting in the formation of desquamating, thickened, inflamed and erythematous plaques. The aim of this investigation was to study the pharmacological activity and safety of three low dose cytokines, Guna-Interleukin 4, Guna-Interleukin 10 and Guna-Interleukin 11 at the concentration of 10 fg/ml in patients affected by moderate to slight psoriasis vulgaris. The multicenter, double-blind, randomized, placebo-controlled clinical trial involved 48 patients who were enrolled and followed up according to a 8-month experimental project. All patients received, according to a cross-over model, either the experimental treatment or placebo, alternatively. Globally, in the 41 evaluated patients it was observed a PASI significant reduction (Friedman test: p=0.00960). The DLQI too decreased significantly in all subjects compared to baseline (Friedman test: p=0.00007). The safety of the treatment with three low dose cytokines administered simultaneously was proved; no adverse event was reported during the whole trial.