The salinity of human body fluid is common knowledge. You can research it yourself if you like. Distilled water in the eye or any mucus membrane, such as the nasal passage, may cause a slight stinging sensation. This can be resolved by adding normal saline to your CS. You can believe it or not. I really don't care. I use CS in normal saline as a nasal spray as well as an eye wash. Perfectly comfortable if you get the right mix. But some people don't mind a little discomfort of straight CS. Do what you like.