Nerve block can eliminate spasms and chronic pain. Kilohertz frequency alternating current (KHFAC) produces a safe and reversible nerve block. However, KHFAC-induced nerve block is associated with an undesirable onset response. Optical inhibition using infrared (IR) laser light can produce nerve block without an onset response, but heats nerves. Combining KHFAC with IR inhibition [alternating current and infrared (ACIR)] produces a rapidly reversible nerve block without an onset response. ACIR can be used to rapidly and reversibly provide onset-free nerve block in the unmyelinated nerves of the marine mollusk Aplysia californica and may have significant advantages over either modality alone. ACIR may be of great clinical utility in the future.