Which of the following hair removal methods requires a trained professional?

Electrolysis is a hair removal method that specifically requires a trained professional due to its technical nature and the equipment involved. This procedure uses an electric current to destroy the hair follicle, and improper use can lead to skin damage, infection, or ineffective hair removal. Professionals are trained to assess the skin type, choose the appropriate settings for the device, and ensure the treatment is performed safely and effectively.

While shaving and waxing can be performed by individuals without formal training, they are not as complex as electrolysis. Shaving is a straightforward process and typically involves minimal risk when proper techniques are used. Waxing can be done at home, but professional waxing services often provide a higher quality and longer lasting result, along with reduced risk of injury or skin irritation. However, electrolysis stands out as the only method mentioned that mandates professional training for safe execution, making it the correct answer.