We all have a large number of small oil glands within the plates of our upper and lower eyelid that help lubricate and hydrate the cornea.   It is very common for these glands to get plugged, harbor bacteria and cause inflammation to the edges of the eyelids.   This causes redness, dandruff-like flaking of skin, and hardened mucous that can stick to the lashes.  This condition is known as blepharitis and it causes a sandy, foreign body sensation -- as if there's something in the eye.