Chemical Composition of Tears

Tears are secretions that clean and lubricate the eyes. Lacrimation or lachrymation (from Latin- lacrima, meaning "tear") is the production or shedding of tears.

Water, Mineral salts, Antibodies & Lysozyme (bactericidal enzyme)

Another interesting discovery about the content of tears was made by Dr. William H. Frey II, a biochemist at the St. Paul-Ramsey Medical Center in Minnesota. He and his team analyzed two types of tears: the emotional ones (crying when emotionally upset and stressed) and the ones arising from irritants (such as crying from onions). They found that emotional tears contained more of the protein-based hormones, prolactin, adrenocorticotropic hormone, and leucine enkephalin (natural painkiller), all of which are produced by our body when under stress. 

It seems as if the body is getting rid of these chemicals through tears. That explains why we usually feel better after a good cry. So, there you go. Cry as much as you want - it is probably good for you. But no cheating by inducing crying with onions. Your tear glands know the difference.

Tears: oils, water, proteins, hormones and mucus.

Tears are not just water. During each blink of the eye, water is mixed with oil and mucous components, and then distributed over the surface of the eye. In people with dry eye, this tear film dries very quickly—about 5 seconds as opposed to 20 seconds normally. By comparing the surface characteristics of complete tear films with those of the component compounds, scientists have been able to develop a more accurate picture of the structure of the film itself and are able to show that the film actually consists of an outer oily layer containing several different types of proteins and mucous. Underneath this, in contact with the eye surface, is a second layer composed of the same components, but in different proportions. Source: http://www.scienceinpublic.com/sciencenow/2005/sophiatragoulias/sophiatragoulias.htm Tears are interesting in themselves. The composition of tears is proteins (lysozyme, lipocalin and lactoferrin), enzymes, lipids, metabolites and electrolytes. The protein concentration differs between emotional tears and the tears produced by irritants. The complex composition of tears, though, differs throughout the daily cycle of human existence.  In healthy mammalian eyes, the cornea is continually kept wet and nourished by basal tears. They lubricate the eye and help to keep it clear of dust. Tear fluid contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Some of the substances in lacrimal fluid fight against bacterial infection as a part of the immune system. In humans, the tear film coating the eye has three distinct layers, from the most outer surface: 1. The lipid layer contains oils secreted by the meibomian glands. The outer-most layer of the tear film, it coats the aqueous layer to provide a hydrophobic barrier that retards evaporation and prevents tears spilling onto the cheek. 2. The aqueous layer contains water and other substances such as proteins (e.g. tear lipocalin, lactoferrin, lysozyme[1] and lacritin) secreted by the glands of Kraus and Wolfring and the lacrimal gland. The aqueous layer serves to promote spreading of the tear film, control of infectious agents and osmotic regulation 3. The mucous layer contains mucin secreted by the conjunctival goblet cells. The inner-most layer of the tear film, it coats the cornea to provide a hydrophilic layer that allows for even distribution of the tear film, as well as mucus covering of the cornea. Source: http://en.wikipedia.org/wiki/Tears Tears are interesting in themselves. The composition of tears is proteins (lysozyme, lipocalin and lactoferrin), enzymes, lipids, metabolites and electrolytes. The protein concentration differs between emotional tears and the tears produced by irritants. The complex composition of tears, though, differs throughout the daily cycle of human existence. The chemical composition of tears reveals an interesting insight. showed that the presence of prolactin in both male and female tears suggests that this substance may function to stimulate tear production. The tears of women between the ages of 15 and 30 years contain greater amounts of prolactin than male tears. Prolactin, as Haeringen notes, increases dramatically in pregnancy.  Source: http://human-nature.com/nibbs/03/crying.html Another interesting discovery about the content of tears was made by Dr. William H. Frey II, a biochemist at the St. Paul-Ramsey Medical Center in Minnesota. He and his team analyzed two types of tears: the emotional ones (crying when emotionally upset and stressed) and the ones arising from irritants (such as crying from onions). They found that emotional tears contained more of the protein-based hormones, prolactin, adrenocorticotropic hormone, and leucine enkephalin (natural painkiller), all of which are produced by our body when under stress. It seems as if the body is getting rid of these chemicals through tears. That explains why we usually feel better after a good cry. So, there you go. Cry as much as you want - it is probably good for you. But no cheating by inducing crying with onions. Your tear glands know the difference.  Source: http://www.scienceiq.com/ShowFact.cfm?ID=64

Sources: Various links cited in text     It depends on the type of the tears! Tears are continually produced in small quantities by the Tear Glands, which are located on the outer side of each eye, slightly above the eye and underneath the eyelid. Tears, which are spread evenly over the front surface of the eye during blinking, clean and lubricate the eye. An important component of tears is lysozyme, a chemical that inhibits bacterial growth on the eye's surface. Some of the tears evaporate, but the remainder are drained into the nose through the Tear Duct, keeping the nose moist. Lysozyme from the tears prevents bacterial growth in the nose as well. Another interesting discovery about the content of tears was made by Dr. William H. Frey II, a biochemist at the St. Paul-Ramsey Medical Center in Minnesota. He and his team analyzed two types of tears: the emotional ones (crying when emotionally upset and stressed) and the ones arising from irritants (such as crying from onions). They found that emotional tears contained more of the protein-based hormones, prolactin, adrenocorticotropic hormone, and leucine enkephalin (natural painkiller), all of which are produced by our body when under stress. It seems as if the body is getting rid of these chemicals through tears. There are three very basic types of tears: Basal tears: In healthy mammalian eyes, the cornea is continually kept wet and nourished by basal tears. They lubricate the eye and help to keep it clear of dust. Tear fluid contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Some of the substances in lacrimal fluid fight against bacterial infection as a part of the immune system. Reflex tears: The second type of tears results from irritation to the eye by foreign particles, or substances such as onion vapors, tear gas or pepper spray. These reflex tears attempt to wash out irritants that may have come into contact with the eye. Crying or weeping (physic tears): The third category, generally referred to as crying or weeping, is increased lacrimation due to strong emotional stress, depression or physical pain. This practice is not restricted to negative emotions; many people have been known to cry when extremely happy or when they are laughing. In humans, emotional tears can be accompanied by reddening of the face and sobbing — cough-like, convulsive breathing, sometimes involving spasms of the whole upper body. Tears brought about by emotions have a different chemical make up than those for lubrication Sources: web and wikipedia