The waterline—a beauty term, not a medical term—is the line of skin between the eyelashes and the eye. Its as close to your eye as you can put eyeliner without actually drawing on your cornea.

Are you supposed to put eyeliner on your waterline?

First things first, you may be wondering if eyeliner is safe for your waterline. The eyes are a sensitive area, so it makes sense that applying eyeliner so close to your eyes could cause irritation. The point is: Yes, eyeliner is safe for your waterline—if youre using the right product.

Where is your upper waterline?

The upper waterline of the eye is the flesh or line of skin under your upper lid. It is usually called as “Tightline” of the eye and is located very close to your lash line. See Also, How to Apply Eyeliner on Waterline.