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

Many over-the-counter products such as bubble baths, room sprays, and lotions claim they contain the pineal hormone melatonin and promote sleep. In this randomized, controlled, double-blind crossover trial we compared the impact of a commercial "sleep lotion" versus a placebo control lotion. Our sample of 63 undergraduate college students scored an average of 6.3 {+/-} 2.7 on the Global Pittsburgh Sleep Quality Index, with 65% above the cutoff of 5 indicating poor sleep quality in the previous 30 days. Participants applied lotions on two different nights, one hour before bedtime. To assess whether melatonin was absorbed through the skin and circulating systemically, we conducted enzyme linked immunosorbent assays on saliva samples to quantitate melatonin levels. We also assessed sleep quality the night after lotion application with a modified Pittsburgh Sleep Quality Index. The melatonin-containing sleep lotion dramatically impacted salivary melatonin levels, increasing them up to [~]1000 fold compared to the placebo control lotion. Sleep quality in the overall group was not impacted by the lotion, but in a subsample of the poor sleepers, the lotion improved sleep quality. High Performance Liquid Chromatography of the sleep lotion revealed the presence of 2.4 {+/-} 0.1 mg melatonin/g lotion, or a 0.24 {+/-} 0.01% formulation. Caution should be taken by consumers using over-the-counter melatonin lotions because the undisclosed dosage is high and well absorbed by the skin. Clinicaltrials.gov ID NCT06053385