Tear composition varies from tear types. Mainly, tears are composed of water, salts, antibodies and lysozymes (antibacterial enzymes). According to a discovery by Dr. William H. Frey II, a bio-chemist from St. Paul Ramsey medical center in Minnesota, the composition of tears caused by emotion differs from that of tears as a reaction to irritations, such as onion fumes, dust or allergy. Emotional tears are composed of more protein-based hormones, such as prolactin, adrenocorticotropic, and leucine enkephalin (a natural pain killer), which is suggested to be the mechanism behind the experience of crying from emotion making an individual feel better.