Transcutaneous electrical nerve stimulation (TENS) is a non-invasive, inexpensive, self-administered technique to relieve pain.

TENS is a method of electrical stimulation which primarily aims to provide a degree of symptomatic pain relief by exciting sensory nerves and thereby stimulating either the pain gate mechanism and/or the opioid system.

The most common TENS parameters used are high-frequency, low-intensity stimulations (>10 Hz, comfortable intensity; high-frequency TENS [HF-TENS]) and low-frequency, high-intensity stimulations (<10 Hz, strong intensity; low-frequency TENS [LF-TENS]). High-frequency transcutaneous electrical nerve stimulations allow depolarization of Aβ fibers, producing segmental analgesia through gate-control mechanisms. On the other hand, the strong stimulations induced by LF-TENS depolarize Aδ and C fibers and decrease pain through activation of descending pain modulating mechanisms originating from the brain stem. Both HF- and LF-TENS produce their hypoalgesic effect through the release of endogenous opioids, with δ-opioid receptors mediating the hypoalgesia of HF-TENS and μ-opioid receptor mediating the hypoalgesia of LF-TENS.