Cryotherapy has been used since the time of ancient Egypt to treat external pain and inflammation. In the nineteenth century, freezing was first used to remove external tissue by using ice and salt. With the advent of liquid nitrogen in the early twentieth century, freezing cells became commonplace. Later in the century, with the development of nitrogen and argon gas, scientists were able to develop the medical technology used in what is now known as cryosurgery.
Salem Press Encyclopedia of Health, 2019. 1p.