The most common cause of red and teary eyes is inflammation. 1. conjunctivitis, which causes conjunctival congestion, tearing, and foreign body sensation. 2. dacryocystitis, lacrimal duct obstruction, and lacrimal duct stenosis, which cause blockage of the lacrimal duct or common lacrimal duct, resulting in obstruction of tear drainage and manifesting as tearing, and stimulation of those inflammatory secretions causing conjunctival congestion. 3. and some serious eye diseases, such as keratitis, which causes congestion and tearing, as well as blurred vision and eye pain. The symptoms are: uveitis, also called iritis, which also causes ciliary congestion, tearing, and eye pain. 4. glaucoma, in acute major attacks of glaucoma, the eye pressure increases, the eye is distended, there is ciliary congestion, tearing, and even symptoms of headache, nausea, and vomiting. So when this happens, it is recommended to go to the hospital for a formal examination.