Cutaneous field stimulation (CFS): a new powerful method to combat itch.

Scratching the skin, while instantly relieving itch, often aggravates itch over time due to skin injury. To relieve itch, without damaging the skin, a new technique termed cutaneous field stimulation (CFS) was developed and tested on 21 subjects. CFS uses a flexible plate with needle-like electrodes (n = 16) to electrically stimulate nerve fibres in the superficial skin. The electrodes were stimulated consecutively (4 Hz per electrode, pulse duration 1 ms, intensity 0.4-0.8 mA, 25 min). CFS resulted in a pricking and burning sensation that usually faded rather quickly. The burning sensation was still present during a selective block of impulse conduction in myelinated fibres indicating that nociceptive C-fibres are activated by CFS. Furthermore, a flare reaction developed around the CFS electrodes indicating activation of axon reflexes in nociceptive C-fibres. Itch, elicited by transdermal iontophoresis of histamine, was abolished within the skin area pre-treated with CFS, and was reduced to 14% of control 10 cm distally. Contralateral effects were small or non-existent. After 4 h, itch was reduced ipsilaterally to 32% of control. In comparison, 2 h after transcutaneous electrical nerve stimulation (TENS; 10-20 mA, 100 Hz, 25 min) ipsilateral itch was reduced to 56% of control. In conclusion, CFS offers a powerful new method for combating itch. It is suggested that CFS acts through endogenous central inhibitory mechanisms that are normally activated by scratching the skin.