Even some cultures and beliefs may have their own interpretations of the significance of tears from the left or right eyes, but these are not based on physiological science.

Tears change when we fall asleep. When you’re asleep, your tear ducts add less protein and water to your tears but boost antibodies. Cells that fight infection also move to your eye.

Even when you’re happy, your eyes are full of tears. They provide moisture and lubrication to help you see and keep your peepers comfortable. What’s in a tear? They’re a mix of: Water, for ...