ORIGIN OF THE EXPRESSIONS "CRACK A SMILE" AND "LOSING FACE"

In the old days, personal hygiene was very poor. As a result, many people had developed acne scars by adulthood. The women used to spread bee's wax  over their faces to smooth out their complexion.
When they were speaking to each another, if one woman stared at another woman's face, she was told: "Mind your own bee's wax.
If the woman smiled, the wax woul crack, hence the term "crack a smile". And sometimes in winter when they sat close to the fire, the wax would melt, hence the expression "loosing face".