From the internet:
"Studies have shown that emotional tears contain more manganese, an element that affects temperament, and more prolactin, a hormone that regulates milk production. Sobbing out manganese and prolactin is thought to relieve tension by balancing the body’s stress levels and eliminating build ups of the chemicals, making the crier feel better."
"But this minor physiological benefit aside, the most likely reason we produce emotional tears is because it’s a means of communication. Before babies can speak, they can cry. The only way for infants to express frustration, pain, fear, or need is to cry. Adults may use crying to bond with other humans. Expressing sadness can prompt comfort and support from peers. Different languages can provide barriers to spoken communication, but emotions are universal. There are also culturally acceptable reasons for crying that bring people together, such as at funerals or weddings."