We bathe children before they go to sleep and everyone cites this as an essential part of a pre-bedtime routine. Why?
Taking a hot bath before bed induces sleep because your body temperature plays a big part in how quickly you fall asleep. At night, there is a slight drop in our body temperature, which signals to our bodies to start producing melatonin, the hormone that induces sleep.
Having a bath raises our body temperature artificially before allowing it to drop again, as you adjust to the cooler environment of the bedroom. It is important to take a bath an hour or two before bed and make the temperature warm rather than hot, so you are comfortable and your body can gently cool down in the run-up to bedtime.