Efficacy of a polyphenolic extract from silver fir (Abies alba) bark on psoriasis: a randomised, double-blind, placebo-controlled trial

Silver fir (Abies alba) bark extract contains a mixture of bioactive polyphenols. We tested their effectiveness in the treatment of psoriasis in order to further investigate the potential topical anti-inflammatory activity of polyphenols by means of a randomized, double-blind, placebo-controlled add-on clinical trial, after having examined their ability to downregulate the expression of IL-1β cytokine in monocyte/macrophage primary cell culture. 61 patients with mild psoriasis met the inclusion criteria and were willing to comply with protocol requirements, were enrolled in the study. The severity of the disease was measured by psoriasis area severity index (PASI). Treatment efficacy was evaluated by assessing erythema (E, 0 to 4-point scale), desquamation (D, 0 to 4-point scale) and induration (I, 0 to 4-point scale) of lesions before and after the treatment. All patients enrolled in the study had symmetrical psoriasis plaques on the skin. All patients received O/V ointment with 2% of silver fir bark extract and/or placebo, respectively. We compared medications by right/left intra-patient comparison, so that the control group was always contralateral of the tested one. Location of the tested or control site was randomised, using a computer-generated randomisation schedule. Silver fir extract was well-tolerated. A superiority of active treatment above placebo, based on the clinical investigational PASI score system was observed by 15 % in all volunteers and in 40% regarding the improvement of psoriasis on elbows. However, statistical analysis showed no significant differences between placebo and active treatment with the extract from silver fir bark (p < 0.05).