Piezo2 channel–Merkel cell signaling modulates the conversion of touch to itch

Loss of touch receptors leads to itch Itch in response to light touch of the skin is an aging-associated problem. This phenomenon is called alloknesis and can become a major medical condition associated with dry skin. Feng et al. discovered that loss or dysfunction of Merkel cells causes scratching in mice (see the Perspective by Lewis and Grandl). Reduction of Merkel cell numbers results in reduced firing patterns and frequencies and changes the activation thresholds of slowly adapting afferent nerve fibers. Like hair cells, Merkel cells are lost with age. A painful scratch will temporarily alleviate itch because it induces enough activity through the remaining Merkel cells. Science , this issue p. 530 ; see also p. 492