Introduction: The natural cyclic tetrahydropyrimidine, ectoine, is a low-molecular, water-binding, organic osmolyte. Previously, topical application of ectoine to healthy human skin was shown to improve skin hydration as well as skin barrier function. Objectives: We therefore speculated that topical application of ectoine would be beneficial for patients with atopic dermatitis (AD), in which a genetically defined defect in skin barrier function is of major pathogenetic relevance. We assessed the efficacy of an ectoine-containing cream (EHK02-01) in the management of 65 patients with mild to moderate AD in a randomized, intra-individual, double-blind, multi-center trial, in which the efficacy of ectoine was compared to a nonsteroidal anti-inflammatory cream previously found to primarily act on skin barrier function and therefore with a comparable mode of action. Methods: Sixty-five patients with mild to moderate AD aged 18-65 years were enrolled. The patients applied EHK02-01 and the control cream on two symmetrical lesions twice daily for 28 days. At the beginning, after 7 and after 28 days, treated skin areas were assessed by modified, objective local SCORAD (Scoring Atopic Dermatitis) and IGA (Investigator's Global Assessment) as well as the patients' judgment of efficacy and their assessment of pruritus. Results: EHK02-01 was found to be very well tolerated. Even more important, efficacy of EHK02-01 treatment was equivalent to that achieved with the reference product. Conclusion: These results indicate that topical treatment with EHK02-01 may represent a novel option for the treatment of patients with AD.