- hormone replacement therapy
- exposure to the wind or dry air, such as constant exposure to a heater during the winter
- allergies
- LASIK eye surgery
- some medications, including antihistamines, nasal decongestants, birth control pills, and antidepressants
- aging
- long-term contact lens wear
- staring at a computer for long hours
- not blinking enough
- chronic allergies
- thyroid disease or other conditions that push the eyes forward
- lupus, rheumatoid arthritis, and other immune system disorders
- exposure keratitis, which occurs from sleeping with your eyes partially open
- vitamin A deficiency, which is unlikely if you get sufficient nutrition