These persons are exempt from this chapter while engaged in the proper discharge of their professional duties:

(1) persons authorized under the laws of this State to practice medicine and surgery;

(2) commissioned medical or surgical officers of the United States Army, Navy, or Marine hospital service;

(3) registered nurses;

(4) students in schools, colleges, and universities who practice barbering only upon students in the school, college, or university premises for the purpose of earning part of their school expenses;

(5) undertakers;

(6) persons authorized by state law to practice cosmetology only when they are practicing in salons or schools of cosmetology.