Topical erythromycin in atopic dermatitis

Staphylococcus aureus (SA) has been shown to play an important role in the pathogenesis of atopic dermatitis (AD). The density of this bacteria correlates directly with cutaneous inflammation and disease severity in patient with AD. That being stated, the use of antibacterial agents should be effective in the control of this disease. Objective of this study was to evaluate efficacy and safety of erythromycin 1% ointment (EO) monotherapy in AD treatment, compared to vehicle (placebo). We performed a 5 weeks, randomized, double-blind, placebo-controlled, crossover study on 38 young patients affected with AD. Patients were randomized in 2 groups: group A and group B. All patients underwent the 1st week wash out period from topical and systemic drugs. During the 2 nd and 3rd week, group A applied EO and group B applied placebo; conversely, during the 4 th and 5 th week, group A applied placebo and group B EO. Before the start of the study and at the end of it, SA skin colonization was investigated in lesional and non lesional areas, through skin swabs plated on to blood agar plate. Moreover tolerability and safety of study products was assessed by patch testing. Clinical evaluation was performed by SCORAD index before, during, and at the end of the study. The study was completed by 19/38 (50,0%) patients. We found that EO was able to decrease Staphylococcus aureus colonization of 64.0% in lesional skin and 100% in non lesional skin of AD patients. In addition, EO was more effective then vehicle alone in reducing SCORAD index. No contact sensitization occurred in any patient and both EO and placebo were defined safe and well tolerated. Nevertheless, although SA infection was markedly reduced, patients showed moderate improvement of clinical conditions after applying EO compared to placebo (9.2% in group A and 6.2% in group B). This demonstrate that EO alone is not effective enough to induce satisfactory improvement of clinical condition. For this reason, therapeutic use of the antibiotic is reasonable in association with topical corticosteroids, in order to reduce their application in acute phase of AD. On the other hand, EO might be considered as a possible single therapy in the subacute phase of the disease, or as a supplementary agent in the rotational therapy from topical anti-inflammatory drugs to moisturizing.