The provisions of this chapter shall not apply to the following persons, while in the proper discharge of their professional duties:
(1) Persons authorized by the law of this state to practice medicine and surgery;
(2) Employees in state penal and charitable institutions;
(3) Registered nurses;
(4) Persons authorized by the law of this state to practice cosmetology.
The provisions of this section shall not be construed to authorize any of the persons exempted by subdivisions (1) to (3), inclusive, of this section to shave or trim the beard or cut the hair of any adult male person for cosmetic purposes.