The causes of tearing eyes include dry-eye syndrome, allergies and eye infections, claims Everyday Health. Irritants, poor eyelid function and blockage of the tear duct can also cause tearing eyes. Tears nourish and lubricate human eyes. However, overproduction of tears leads to tearing eyes.
Dry-eye syndrome is commonly caused by keratoconjunctivitis sicca, which is the production of tears without enough water, explains Everyday Health. Dry-eye syndrome stimulates overproduction of tears by the lacrimal glands. Too many tears overwhelm the natural drainage system of the eye leading to tearing eyes. Dry eyes are more common among older people because the production of tears reduces with increased age. Aside from tearing eyes, other symptoms of dry-eye syndrome can be itchy eyes, blurred vision or burning eyes.
Allergies cause tearing eyes when a person reacts to allergens, which cause the eyes to redden and become irritated, says Everyday Health. This stimulates tear production, burning and itching. The causes of allergic eye symptoms include grass, tree and weed pollens, as well as indoor substances such as dust mites and molds. False allergens such as aerosol sprays, perfumes and exhaust fumes also cause tearing eyes.
Tearing eyes can also occur as part of the body's response to eye infections such as blepharitis and conjuctivitis, notes Everyday Health. The overproduction of tears washes away germs and lubricates the eyes.