Tears are made up of tear fluid secreted by the lacrimal glands. Tear fluid contains sodium chloride, mucus, antibodies and lysozyme, an enzyme that helps to eliminate bacteria. Tears clean the eye, protect it and lubricate its surface, the cornea. Tears also help oxygenate the cornea. Tears also remove impurities that enter the eye by accident. Over time, the activity of the tear glands can decrease, causing the eye to dry out, leading to infections and irritation of the eye. When tear production is insufficient, it is often referred to as dry eye syndrome. There are 3 types of tears: the permanent tear which helps to moisturize and protect the eye, the reflex tear which comes in response to an irritation and the emotional tear. The composition of the tear varies when it is triggered by emotion. The tear then becomes loaded with proteins and hormones, including prolactin and encephalic leucine, which acts on pain.