Itch is an unpleasant cutaneous sensation that evokes the desire to scratch.
In a healthy situation, itch is a positive stimulus for eliminating environmental irritants such as parasites or plant particles and leads to avoidance of the irritants that lead to itch, such as poison ivy.
Healthy skin depends on Ca⁺⁺ for it’s structure. Transient Receptor Proteins (TRP) ion channels have emerged as cellular sensors for thermal, chemical and mechanical stimuli and are major contributors to Ca⁺⁺ signaling, playing an important role in diverse physiological and pathological processes. One specific protein, TRPV3, helps the skin perceive sensations such as temperature and itch.
In certain diseases, TRPV3 is out of balance, and leads to excess Ca⁺⁺ influx into the cells. The excess Ca⁺⁺ influx negatively impacts the structure of the skin due to an increase in keratinocytes (also called hyperkeratosis), inflammation and afferent nerve endings stimulation, increasing itch sensation.
Because of the increased sensation of itch, persons with these diseases often scratch the affected area, harming local tissue and further contributing to the cycle of chronic, debilitating itch.