Hydration is a more contentious subject than you might think. Despite what you've heard, the "eight glasses a day" recommendation doesn't really have much merit -- in fact, you can comfortably go up to a gallon daily and be just fine, if not in better health than you ever were before.
So water is good for you, duh. But outside of total dehydration, what are some signs that you might not be giving your body the H2O it needs?
Your skin dries out
Lips feeling chapped? You're likely dehydrated. Pinch the skin on the back of your hand. If it looks and stays like a tent (it's literally called "tenting") and takes its time going back to normal, you guessed it: drink more water. Other dehydration indicators include brittle nails, a sticky feeling in your eyes, and dry mouth.
"When the body is dehydrated for any reason, the skin, which is the largest organ of the body, can show signs of depletion. The skin appears dull and lacks the snap or turgor that it should have," says Dr. Mirwat Sami, adding, "The mouth will be dry, saliva will be decreased in quantity, and the lips can appear chapped. Also, the eyes will be dry with decreased tear production, that is the normal baseline tears to lubricate the eyeball will be decreased."