The use of water to improve health is called hydrotherapy. After taking a hot shower, end on a cold rinse. It doesn’t have to be torturous, it just needs to be a temperature difference. This creates a strong pumping action which stimulates the immune system, decreases inflammation, and improves metabolism among other things.
Just try it. You’ll walk out of your shower warmer than if you didn’t, I guarantee it. This is because the cold water drives your circulation back to your core to keep you warm.