Mo. Rev. Stat. § 329.034: Shampooing — no license required, when.

Notwithstanding any other provision of law, the division of professional registration shall not require any person who engages solely in shampooing under the supervision of a licensed barber or cosmetologist to be licensed as a barber or cosmetologist. For purposes of this section, "shampooing" means the act of washing or cleansing hair with shampoo for compensation.