Re: Why do my eyes water when I am really tired and have to stay awake?

Hi Patricia-

My best guess for why your eyes water when you're so tired is that they are drying out. Your eyes respond to any irritation (dust, hair, or dryness) by producing tears from the lacrimal gland. When your eyes have been open too many hours straight, they can get pretty dried out!

(You can click on the image to see a brief summary about the lacrimal gland)

I hope that helps!

-Alex
cgoddard@fas.harvard.edu