[ELI5] Why do glasses get dirty while you sleep?

Question

When I wake up the part of glasses that’s closest to my nose always gets dirty with an oily thing even if I don’t have them on

I don’t sleep with my glasses on

In: Chemistry

Answer 1

First off, you shouldn’t sleep with your glasses on (Assuming it’s not just a quick nap, such as when on a bus or plane).

I don’t sleep with my glasses on, but I do notice that often times the upper middle portions of the glass will get dirty, likely as they are close to my eye brows, which could transfer oils to the glass. Also likely due to those areas being closest to the point in which I grab my glasses (The bridge).