Which process falls under medical treatment and is illegal for cosmetologists to perform without supervision?

The process that falls under medical treatment and is illegal for cosmetologists to perform without supervision is cutting. This activity can involve procedures that may lead to the risk of injury or infection, especially if it involves the skin or nails in a way that requires more specialized knowledge and training.

For instance, cutting the skin around the nails (like during a manicure) can present risks such as bleeding or the introduction of bacteria, leading to infections. Because of these risks, regulations typically require that such procedures be performed under the supervision of a licensed medical professional or a licensed practitioner who has the authority to conduct medical treatments.

The other options, such as filing, planing, and soaking, are generally considered to be safe cosmetic practices that do not penetrate the skin and thus do not carry the same legal medical implications or regulations. These processes can be performed safely by trained nail technicians without the need for a medical license or supervision.