痒感多由蚊虫叮咬、过敏等引发的局部炎症产生，通过细直径慢神经元经脊髓丘脑束传导至大脑。而皮肤中的机械感受器能感知触摸和震动，其信号通过粗直径快神经元经背柱传导。脊髓内两类神经元通过中间神经元交联，触摸信号会激活抑制痒感传导的神经元，这就是 “闸门理论”—— 触摸能 “关闭” 痒感通道。此外，触摸刺激大脑深层结构会反向抑制痒感传递，功能性磁共振成像研究还显示，挠痒能激活大脑奖励中枢，带来愉悦感。

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