What is this dark circles under the eyes business? Are you referring to one of the signs of dehydration? My two and a half year old CAH daughter often has dark circles under her eyes, but then her dad and I do, too, so I think it's probably mostly heredity. All three of us look like racoons when we're tired or battling a cold/flu. And she doesn't exhibit other signs of dehydration like dry mouth and eyes, smaller urine output, etc. What have you been told?