Nothing in sections 155A.21 to 155A.36 prohibits services in cases of emergency where compensation or other reward is not received, nor in domestic service, nor in the practice of medicine, surgery, dentistry, podiatry, osteopathic medicine, chiropractic, or barbering. This section shall not be construed to authorize any of the persons so exempted to wave the hair, or to color, tint, or bleach the hair, in any manner.