Melatonin is a hormone that promotes sleep that is available without a prescription in the United States. In addition to oral supplements, melatonin can be purchased in the form of lotions and bubble baths with unknown dosage and no frequency or age recommendations. In this study, researchers will examine how quickly melatonin in lotion and bubble bath is absorbed compared to oral tablets, as well as how long the melatonin lasts in the body.

Melatonin is a hormone that promotes sleep that is available without a prescription in the United States. In addition to oral supplements, melatonin can be purchased in the form of lotions and bubble baths with unknown dosage and no frequency or age recommendations. A previous study (unpublished) has shown that a small amount of an over-the-counter lotion increases salivary melatonin levels by up to 1000 fold, a startling amount. Researchers will characterize the time course of the absorption and metabolism of lotion- and bubble bath-based melatonin compared to oral tablets in healthy 18-22 year olds.

The peak level, time to peak level and half-life of melatonin will be compared between the administration routes using a within-person (repeated measures) design and saliva sampling over 48 hours. Participants can choose specific days to participate within a one-month window, with a maximum of four sampling periods. All participants will collect control saliva samples (no melatonin treatment) one night at 10 PM and 4 AM. Participants will be asked to have two treatments 1) oral melatonin and 2) either lotion melatonin or bubble-bath melatonin. Participants can indicate if they have a preference for lotion vs. bubble bath or if they are willing to undergo both lotion and bubble bath treatments (adding a fourth sampling period). Order will be randomized.

For the treatments, saliva sampling times are as follows: Prior to melatonin administration (10 AM), then 15 min, 30 min, 45 min, 60 min, 90 min, 2 hours, 3 hours, 4 hours, 6 hours, 8 hours, 12 hours (10 PM), 18 hours (4 AM), 24 hours, 36 hours, and 48 hours after administration. Samples will be frozen at the participant's home until returned to the researchers at a later date. Melatonin in saliva samples will be quantitated via Enzyme Linked Immunosorbent Assay.

Inclusion Criteria:

• University of Redlands student

Exclusion Criteria:

• Allergies or sensitivities to scented lotions or bath products
• Pregnancy

Upload salivary melatonin levels and side effect frequencies (all collected IPD) to National Sleep Research Resource (https://sleepdata.org/)

After relevant publication. Data will remain at the National Sleep Research Resource following their policy for keeping records.

According to the National Sleep Research Resource