Which of the following treatments is least invasive?

Microcurrent therapy is considered the least invasive treatment among the listed options because it utilizes low-level electrical currents to stimulate facial muscles and promote healing without causing significant tissue damage or requiring downtime. This non-invasive approach focuses on enhancing facial contours and overall skin tone, which can be done comfortably in a clinical setting.

In contrast, chemical peels involve the application of acidic solutions to exfoliate the skin, which can lead to redness and peeling that require downtime for recovery. Laser resurfacing is designed to remove the outer layer of skin or stimulate collagen production through more aggressive means, resulting in a more invasive procedure with potential side effects such as swelling and recovery time. Ultrasound therapy, while also non-invasive, typically penetrates deeper into the skin than microcurrent therapy, meaning it may have more associated discomfort or skin response, particularly through thermal effects.

Thus, microcurrent therapy stands out as the gentler choice, making it the least invasive option in this context.