Spa hydrotherapy isn’t exactly a modern treatment. In fact, people have been using it as a form of medicine in the western world since at least the 18th century. In its modern form, it is designed to make your skin glow. This is one of the easiest spa treatments you can recreate at home. Just stand underneath your shower while it is hot, then switch to the coldest setting, and repeat a few times. Voila, hydrotherapy.