One extreme example is a psychological condition called delusory parasitosis where people believe their bodies are infested with mites or fleas scurrying over and under their skin, making them itch incessantly.

端例子是种叫做妄想性寄生虫病心理况，人认为身体被螨虫或跳蚤滋生，在皮肤上下窜动，使不停地发痒。