Papers of the Week

Slowly depolarizing currents applied for 1 min have been shown to activate C-nociceptors and provoke increasing pain in patients with neuropathy. This study examined the effect of transcutaneous slowly depolarizing currents on pruritus in patients with atopic dermatitis. C-nociceptor-specific electrical stimu-lation was applied to areas of eczema-affected and non-affected skin in 26 patients with atopic dermatitis. Single half-sine wave pulses (500 ms, 0.2-1 mA) induced itch in 9 patients in the eczema (numerical rating scale 5 ± 1), but pain in control skin (numerical rating scale 6 ± 1). Sinusoidal stimuli (4 Hz, 10 pulses, 0.025-0.4 mA) evoked itch in only 3 patients, but on delivering pulses for 1 min (0.05-0.2 mA) approximately 50% of the patients (n = 12) reported itch with numerical rating scale 4 ± 1 in areas of eczema-affected skin. The number of patients reporting itch increased with longer stimulation (p < 0.005). These results indicate a reduced adaptation of peripheral C-fibres conveying itch in patients with AD. Also, sensitized spinal itch processing may underlie chronic itch in these patients, who might benefit from centrally acting antipruritic therapy.