Watering eye ,also known as epiphora or tearing, is a condition in which there is an overflow of tears onto the face, often without a clear explanation. There are two main causes of watering eyes - blocked tear ducts or excessive production of tears. If a patient's tear ducts are narrowed or blocked their tears will not be able to drain away and will build up in the tear sac. cause of over-production of tears:Some chemicals, such as fumes, and even onions,Infective conjunctivitis,Allergicconjunctivitis,An injury to the eye, such as a scratch or a bit of grit (tiny pebble or piece of dirt),Trichiasis - inward-growing eyelashes, often caused by marginal entropion (the eye lid turns in at the edges towards the eye),Ectropion - this is when the lower eyelid turns outwards