I've been thinking about osmosis as a way to rehydrate. In other words, besides drinking fluids, fluids enter the body via contact with the body's surface - without entering the digestive system. I don't know how much it happens with humans or how significant it is, but many plants seem to respond to contact with water (through the surface of leaves and bark) in addition to uptake through the roots, as do insects and birds. I have no references for this - it's just observation and pondering in the heat of August in Texas. Rain is good.

I heard a factoid about a year ago that you can warm up by keeping even a small part of the body warm. For example, a pair of gloves or a scarf affects the overall temperature of the body. I've found this to be true in lowering one's temperature as well, that a cold wash cloth applied to the back of the neck, or running the wrists under cool water can cool down one's overall temperature. Washing dishes by hand in hot (not too hot!) water can have warming and relaxing effects. In the past, poultices (fabric cloths, or sacks) of herbs were warmed and applied to ease pain. Chilled poultices were used to reduce fevers and swelling. Some viruses and bacteria (and the cells of certain tumors) that thrive at normal human temperatures are diminished by temperature change. Regular swims in chilly water or soaking in hot baths can have positive effects on maintaining one's overall health.