Regardless of whether you’re crying or your eyes are watering, the liquid in your eyes is created in the same way. These tears help protect your eyes, keeping them moist and washing out dust and anything else that might get in there.
Tears come out of tear glands, or lacrimal glands, found in your upper eyelids. From here, the tears can wash over your eyes. Some tears drain out of the eyes through tear ducts – tiny tubes that run between your eyes and nose, located at the corner of each eye. If your tears are flowing too quickly for your ducts, however, then your tears flow down your face. Because tear ducts run to your nose, you may notice that your nose often begins to run when you are crying.
But back to the question at hand – why exactly do eyes water in the first place? Anything that irritates the eye – be it dirt, an eyelash, or a cloud of smoke – will cause it to water in an effort to flush it out. Even the fumes of onions contain tiny chemicals that irritate your eye, which causes you to cry while cutting the vegetables. Tearing up also protects the eye from getting too dry – so cold air and wind may also induce watery eyes in an effort to keep eyes moist.