Tearing or watery eyes is excessive tearing, which is generated when the duct that drains tears into the nose is clogged or malfunctioning. One of the most common causes of tearing is dry eyes. Dryness causes the eyes to produce too many tears and, therefore, excess tearing occurs. Irritation, infection or the growth of eyelashes into the eye may develop watery eyes. Although there are other common causes such as allergies to dust and mold that can cause conjunctivitis or tearing.