Impact of an over-the-counter "sleep lotion" on human salivary melatonin levels and sleep quality: a randomized controlled trial.

Objective: To compare the impact of a commercial "sleep lotion" versus a placebo control lotion on salivary melatonin and sleep quality.

Methods: The presence of melatonin in the lotion was confirmed and quantitated with High Performance Liquid Chromatography (HPLC). In this randomized, controlled, double-blind crossover trial, undergraduate student participants applied lotions on two separate nights and we quantitated melatonin in saliva samples with enzyme linked immunosorbent assays. We also assessed sleep quality with a modified Pittsburgh Sleep Quality Index.

Clinicaltrials: gov ID NCT06053385.

Results: Sixty-three participants (age 20.5 ± 1.2 years; 81% female) enrolled in the study and provided at least one saliva sample. The sleep lotion contained 0.24 ± 0.01% melatonin (g/100 g lotion) which dramatically impacted salivary melatonin levels, increasing them up to ~1000 fold compared to the placebo lotion (n = 36 participants with all six timepoints). The lotion improved sleep quality in a subsample of the poor sleepers (n = 18). However, the sleep quality in the overall sample was not significantly different on the active versus placebo lotion nights.

Conclusion: In a small undergraduate student sample, a commercial melatonin-containing lotion improved sleep in those with poor sleep quality. Caution should be taken by consumers using over-the-counter melatonin lotions because the undisclosed dosage can be high and well absorbed by the skin.