I have had dry eye before but usually just brief. why?

Varies: Could be allergens or other irritants that inflame the surface of the eye causing symptoms similar to chronic dry eye. If its only brief then not likely anything of concern. You can use over-the-counter artificial tears for short term problems. If it becomes chronic then see an eye doctor.

Dry eye causes: Dry eyes can be briefly occur from: staring; clogged meibomian glands; allergies. There are many therapy options: best to start naturally (warm compresses, diluted baby shampoo scrubs) & move up a "ladder approach" to antibiotic cream, otc artificial tears. More info if needed at: http://eyedoc2020.Blogspot.Com/2013/04/best-step-ladder-approach-to-dry-eye.Html i hope this helps you!