What causes Watery Eyes?

Dear Ask The Doctor: I wake up in the middle of the night and my left eye is leaking. Why is it doing that?

Dear Cynthia: Watery eyes occur when your body makes more tears than you lose through evaporation or drainage. Watery eyes or excess tearing may happen naturally in response to emotions or to cold, windy weather. Otherwise, persistent watery eyes can have many causes, including allergies and infections. A blocked tear duct is a common cause of watery eyes. Complications from dry eyes or eye irritation can trigger the release of a large amount of tears in an attempt to lubricate your eyes. The excess tears overwhelm the drainage system, causing watery eyes. Usually watery eyes resolve on its own and no treatment is required.