Writing for The Conversation, Timothy Hearn, a lecturer in Bioinformatics, said: “Bright light in the evening signals to the brain’s internal body clock that it is still daytime. This delays the release of melatonin, a hormone that helps regulate sleep and is often described as the body’s ‘darkness signal’.
Article source: https://www.huffingtonpost.co.uk/entry/showering-in-dark-benefits_uk_6995a69ee4b0d22a8030f178