I will pass this on as I heard it years ago from a woman that had a Maltese coming in for boarding where I used to work. She brought jugs of distilled water and requested we give that water to her rather than the tap water at the kennel. "Why" we asked. She replied, "It clears up and prevents the stains under her eyes". She was a show dog at one time and that was what the handler told her to do to keep her eyes pretty. I will say this dog did not have any tear stains which are so prevalent on all little dogs with long coats and big eyes. I would guess there are no minerals like iron in it. It makes perfect sense to me.