BACKGROUND: Skin cancer is an increasing problem in modern dermatology. Earlier studies have shown protective effects against ultraviolet radiation (UVR)-induced skin damage by topical treatment with melatonin. However, the potential sedative effects of full body topical application of melatonin have never been investigated. Objectives The aim of this study was to assess the degree of cognitive dysfunction when using melatonin cream as full body topical application.

METHODS: In a randomized, placebo-controlled, double-blind crossover study in healthy volunteers, the degree of cognitive dysfunction when using cream containing 12.5% melatonin as full body application was assessed. A group of ten volunteers had melatonin cream 12.5% applied on 80% of their body surface area, and degree of cognitive dysfunction was assessed using a test battery consisting of Karolinska sleepiness scale (KSS), Finger tapping test (FTT) and Continuous Reaction time (CRT).

RESULTS: No significant effects on cognitive parameters were found. However, great inter-individual variations on cognitive parameters were observed.

CONCLUSION: This study was the first to assess degree of cognitive dysfunction resulting from application of melatonin cream on a full body surface area. The results support that melatonin is a safe drug for dermal application even in a high dosage.